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Robert Boyle

Robert Boyle was descended from a family who, in Saxon times, held
land in the county of Hereford, and whose name in the Doomsday Book is
written Biuvile. His father was Richard Boyle, Earl of Cork, to whom
the fortunes of the family were largely due. Richard Boyle was born in
the city of Canterbury, October 3, 1566. He was educated at Bene't
College (now Corpus Christi College), Cambridge, and afterwards became
a member of the Middle Temple. Finding his means insufficient for the
prosecution of his legal studies, he determined to seek his fortune
abroad. In 1595 he married, at Limerick, one of the daughters of
William Apsley, who brought him land of the value of L500 per annum.
In his autobiography the Earl of Cork writes:--

When first I arrived at Dublin, in Ireland, the 23rd of June
1588, all my wealth then was twenty-seven pounds three shillings
in money, and two tokens which my mother had given me, viz. a
diamond ring, which I have ever since and still do wear, and a
bracelet of gold worth about ten pounds; a taffety doublet cut
with and upon taffety, a pair of black velvet breeches laced, a
new Milan fustian suit laced and cut upon taffety, two cloaks,
competent linen, and necessaries, with my rapier and dagger. And
since, the blessing of God, whose heavenly providence guided me
hither, hath enriched my weak estate, in beginning with such a
fortune, as I need not envy any of my neighbours, and added no
care or burthen of my conscience thereunto. And the 23rd of
June, 1632, I have served my God, Queen Elizabeth, King James,
and King Charles, full forty-four years, and so long after as it
shall please God to enable me.

Richard Boyle's property in Ireland increased so rapidly that he was
accused to Queen Elizabeth of receiving pay from some foreign power.
When about to visit England in order to clear himself of this charge,
the rebellion in Munster broke out; his lands were wasted, and his
income for the time destroyed. Reaching London, he returned to his old
chambers in the Middle Temple, until he entered the service of the
Earl of Essex, to whom the government of Ireland had been entrusted.
The charges against him were then resumed, and he was made a prisoner,
and kept in confinement until the Earl of Essex had gone over to
Ireland. At length he obtained a hearing before the queen, who fully
acquitted him of the charges, gave him her hand to kiss, and promised
to employ him in her own service; at the same time she dismissed Sir
Henry Wallop, who was Treasurer for Ireland, and prominent among
Boyle's accusers, from his office.

A few days afterwards, Richard Boyle was appointed by the queen Clerk
to the Council of Munster, and having purchased a ship of Sir Walter
Raleigh, he returned to Ireland with ammunition and provisions.

"Then, as Clerk of the Council, I attended the Lord President in all
his employments, and waited upon him at the siege of Kingsale, and was
employed by his Lordship to her Majesty, with the news of that happy
victory; in which employment I made a speedy expedition to the court;
for I left my Lord President at Shannon Castle, near Corke, on the
Monday morning, about two of the clock, and the next day, being
Tuesday, I delivered my packet, and supped with Sir Robert Cecil,
being then principal Secretary of State, at his house in the Strand;
who, after supper, held me in discourse till two of the clock in the
morning; and by seven that morning called upon me to attend him to the
court, where he presented me to her Majesty in her bed-chamber, who
remembered me, calling me by my name, and giving me her hand to kiss,
telling me that she was glad that I was the happy man to bring the
first news of that glorious victory ... and so I was dismissed with
grace and favour."

In reading of this journey from Cork to London, it is almost necessary
to be reminded that it took place two hundred and fifty years before
the introduction of steam-boats and railways. At the close of the
rebellion, Richard Boyle purchased from Sir Walter Raleigh all his
lands in Munster; and on July 25, 1603, he married his second wife,
Catharine, the only daughter of Sir Geoffrey Fenton, principal
Secretary of State, and Privy Councillor in Ireland, "with whom I
never demanded any marriage portion, neither promise of any, it not
being in my consideration; yet her father, after my marriage, gave me
one thousand pounds in gold with her. But that gift of his daughter
unto me I must ever thankfully acknowledge as the crown of all my
blessings; for she was a most religious, virtuous, loving, and
obedient wife unto me all the days of her life." He was knighted by
the Lord Deputy of Ireland, Sir George Carew, on his wedding-day; was
sworn Privy Councillor of State of the Kingdom of Ireland in 1612;
created Lord Boyle, Baron of Youghall, September 29, 1616; Lord
Viscount of Dungarvon and Earl of Cork, October 26, 1620; one of the
Lords Justices of Ireland, with a salary of L1200 per annum, in 1629;
and Lord High Treasurer of Ireland, November 9, 1631.

Robert Boyle, the seventh son of the Earl of Cork, was born January
25, 1627. His mother died February 16, 1630. The earl lived in
prosperity in Ireland till the breaking out of the rebellion in 1641,
and died at Youghall in September, 1643. It is said that when Cromwell
saw the vast improvements which the earl had made on his estate in
Munster, he declared that "if there had been an Earl of Cork in every
province, it would have been impossible for the Irish to have raised a

At a very early age Robert was sent by his father to a country nurse,
"who, by early inuring him, by slow degrees, to a coarse but cleanly
diet, and to the usual passion of the air, gave him so vigorous a
complexion that both hardships were made easy to him by custom, and
the delights of conveniences and ease were endeared to him by their
rarity." Making the acquaintance of some children who stuttered in
their speech, he, by imitation, acquired the same habit, "so
contagious and catching are men's faults, and so dangerous is the
familiar commerce of those condemnable customs, that, being imitated
but in jest, come to be learned and acquired in earnest." Before going
to school he studied French and Latin, and showed considerable
aptitude for scholarship. He was then sent to Eton, where his master
took much notice of him, and "would sometimes give him unasked
play-days, and oft bestow upon him such balls and tops and other
implements of idleness as he had taken away from others that had

unduly used them."

While at school, in the early morning, a part of the wall of the
bedroom, with the bed, chairs, books, and furniture of the room above,
fell on him and his brother. "His brother had his band torn about his
neck, and his coat upon his back, and his chair crushed and broken
under him; but by a lusty youth, then accidentally in the room, was
snatched from out the ruins, by which [Robert] had, in all
probability, been immediately oppressed, had not his bed been
curtained by a watchful Providence, which kept all heavy things from
falling on it; but the dust of the crumbled rubbish raised was so
thick that he might there have been stifled had not he remembered to
wrap his head in the sheet, which served him as a strainer, through
which none but the purer air could find a passage." At Eton he spent
nearly four years, "in the last of which he forgot much of that Latin
he had got, for he was so addicted to more solid parts of knowledge
that he hated the study of bare words naturally, as something that
relished too much of pedantry to consort with his disposition and
designs." On leaving Eton he joined his father at Stalbridge, in
Dorsetshire, and was sent to reside with "Mr. W. Douch, then parson of
that place," who took the supervision of his studies. Here he renewed
his acquaintance with Latin, and devoted some attention to English
verse, spending some of his idle hours in composing verses, "most of
which, the day he came of age, he sacrificed to Vulcan, with a design
to make the rest perish by the same fate." A little later he returned
to his father's house in Stalbridge, and was placed under the tutelage
of a French gentleman, who had been tutor to two of his brothers.

In October, 1638, Robert Boyle and his brother were sent into France.
After a short stay at Lyons, they reached Geneva, where Robert
remained with his tutor for about a year and three quarters. During
his residence here an incident occurred which he regarded as the most
important event of his life, and which we therefore give in his own

"To frame a right apprehension of this, you must understand that,
though his inclinations were ever virtuous, and his life free from
scandal and inoffensive, yet had the piety he was master of already so
diverted him from aspiring unto more, that Christ, who long had lain
asleep in his conscience (as He once did in the ship), must now, as
then, be waked by a storm. For at a time which (being the very heat of
summer) promised nothing less, about the dead of night, that adds most
terror to such accidents, [he] was suddenly waked in a fright with
such loud claps of thunder (which are oftentimes very terrible in
those hot climes and seasons), that he thought the earth would owe an
ague to the air, and every clap was both preceded and attended with
flashes of lightning, so frequent and so dazzling that [he] began to
imagine them the sallies of that fire that must consume the world. The
long continuance of that dismal tempest, where the winds were so loud
as almost drowned the noise of the very thunder, and the showers so
hideous as almost quenched the lightning ere it could reach his eyes,
confirmed him in his apprehensions of the day of judgment's being at
hand. Whereupon the consideration of his unpreparedness to welcome
it, and the hideousness of being surprised by it in an unfit
condition, made him resolve and vow that, if his fears were that night
disappointed, all his further additions to his life should be more
religiously and watchfully employed. The morning came, and a serene,
cloudless sky returned, when he ratified his determinations so
solemnly, that from that day he dated his conversion, renewing, now he
was past danger, the vow he had made whilst he believed himself to be
in it; and though his fear was (and he blushed it was so) the occasion
of his resolution of amendment, yet at least he might not owe his more
deliberate consecration of himself to piety to any less noble motive
than that of its own excellence."

After leaving Geneva, he crossed the Alps and travelled through
Northern Italy. Here he spent much time in learning Italian; "the rest
of his spare hours he spent in reading the modern history in Italian,
and the new paradoxes of the great stargazer Galileo, whose ingenious
books, perhaps because they could not be so otherwise, were confuted
by a decree from Rome; his highness the Pope, it seems, presuming, and
that justly, that the infallibility of his chair extended equally to
determine points in philosophy as in religion, and loth to have the
stability of that earth questioned in which he had established his

Having visited Rome, he at length returned to France, and was detained
at Marseilles, awaiting a remittance from the earl to enable him to
continue his travels. Through some miscarriage, the money which the
earl sent did not arrive, and Robert and his brother had to depend on
the credit of the tutor to procure the means to enable them to return
home. They reached England in the summer of 1644, "where we found
things in such confusion that, although the manor of Stalbridge were,
by my father's decease, descended unto me, yet it was near four months
before I could get thither." On reaching London, Robert Boyle resided
for some time with his sister, Lady Ranelagh, and was thus prevented
from entering the Royalist Army. Later on he returned for a short time
to France; visited Cambridge in December, 1645, and then took up his
residence at Stalbridge till May, 1650, where he commenced the study
of chemistry and natural philosophy.

It was in October, 1646, that Boyle first made mention of the
"invisible college," which afterwards developed into the Royal
Society. Writing to a Fellow of Magdalen College, Cambridge, in
February, 1647, he says, "The corner-stones of the invisible, or, as
they term themselves, the philosophical college, do now and then
honour me with their company." It appears that a desire to escape from
the troubles of the times had induced several persons to take refuge
in philosophical pursuits, and, meeting together to discuss the
subjects of their study, they formed the "invisible college." Boyle
says, "I will conclude their praises with the recital of their
chiefest fault, which is very incident to almost all good things, and
that is, that there is not enough of them." Dr. Wallis, one of the
first members of the society, states that Mr. Theodore Hooke, a German
of the Palatinate, then resident in London, "gave the first occasion
and first suggested those meetings and many others. These meetings we
held sometimes at Dr. Goddard's lodging, in Wood Street (or some
convenient place near), on occasion of his keeping an operator in his
house, for grinding glasses for telescopes and microscopes, and
sometimes at a convenient place in Cheapside; sometimes at Gresham
College, or some place near adjoining. Our business was (precluding
theology and State affairs) to discourse and consider of philosophical
inquiries, and such as related thereunto; as physic, anatomy,
geometry, astronomy, navigation, statics, magnetics, chemics,
mechanics, and natural experiments, with the state of these studies as
then cultivated at home and abroad. About the year 1648-49 some of us
being removed to Oxford, first Dr. Wilkins, then I, and soon after Dr.
Goddard, our company divided. Those in London continued to meet there
as before, and we with them when we had occasion to be there. And
those of us at Oxford, with Dr. Ward, since Bishop of Salisbury, Dr.
Ralph Bathurst, now President of Trinity College in Oxford, Dr. Petty,
since Sir William Petty, Dr. Willis, then an eminent physician in
Oxford, and divers others, continued such meetings in Oxford, and
brought those studies into fashion there; meeting first at Dr.
Petty's lodgings, in an apothecary's house, because of the convenience
of inspecting drugs and the like, as there was occasion; and after his
remove to Ireland (though not so constantly) at the lodgings of Dr.
Wilkins, then Warden of Wadham College; and after his removal to
Trinity College in Cambridge, at the lodgings of the Honourable Mr.
Robert Boyle, then resident for divers years in Oxford. These meetings
in London continued, and after the king's return, in 1660, were
increased with the accession of divers worthy and honourable persons,
and were afterwards incorporated by the name of the Royal Society,
and so continue to this day."

Boyle was only about twenty years of age when he wrote his "Free
Discourse against Swearing;" his "Seraphic Love; or, Some Motives and
Incentives to the Love of God;" and his "Essay on Mistaken Modesty."
"Seraphic Love" was the last of a series of treatises on love, but the
only one of the series that he published, as he considered the others
too trifling to be published alone or in conjunction with it. In a
letter to Lady Ranelagh, he refers to his laboratory as "a kind of
Elysium," and there were few things which gave him so much pleasure as
his furnaces and philosophical experiments. In 1652 he visited
Ireland, returning in the following summer. In the autumn he was again
obliged to visit Ireland, and remained there till the summer of 1654,
though residence in that country was far from agreeable to him. He
styled it "a barbarous country, where chemical spirits were so
misunderstood, and chemical instruments so unprocurable, that it was
hard to have any hermetic thoughts in it." On his return he settled in
Oxford, and there his lodgings soon became the centre of the
scientific life of the university. Boyle and his friends may be
regarded as the pioneers of experimental philosophy in this country.
To Boyle the methods of Aristotle appeared little more than
discussions on words; for a long time he refused to study the
philosophy of Descartes, lest he should be turned aside from reasoning
based strictly on the results of experiment. The method pursued by
these philosophers had been fully discussed by Lord Bacon, but at best
his experimental methods, though most complete and systematic, existed
only upon paper, and it was reserved for Boyle and his friends to put
the Baconian philosophy into actual practice.

It was during his residence at Oxford that he invented the air-pump,
which was afterwards improved for him by Hooke, and with which he
conducted most of those experiments on the "spring" and weight of the
air, which led up to the investigations that have rendered his name
inseparably connected with "the gaseous laws." The experiments of
Galileo and of Torricelli had shown that the pressure of the air was
capable of supporting a column of water about thirty-four feet in
height, or a column of mercury nearly thirty inches high. The younger
Pascal, at the request of Torricelli, had carried a barometer to the
summit of the Puy de Dome, and demonstrated that the height of the
column of mercury supported by the air diminishes as the altitude is
increased. Otto von Guericke had constructed the Magdeburg
hemispheres, and shown that, when exhausted, they could not be
separated by sixteen horses, eight pulling one way and eight the
other. He was aware that the same traction could have been produced by
eight horses if one of the hemispheres had been attached to a fixed
obstacle; but, with the instincts of a popular lecturer, he considered
that the spectacle would thus be rendered less striking, and it was
prepared for the king's entertainment. Boyle wished for an air-pump
with an aperture in the receiver sufficiently large for the
introduction of various objects, and an arrangement for exhausting it
without filling the receiver with water or otherwise interfering with
the objects placed therein. His apparatus consisted of a large glass
globe capable of containing about three gallons or thereabouts,
terminating in an open tube below, and with an aperture of about four
inches diameter at the top. Around this aperture was cemented a turned
brass ring, the inner surface being conical, and into this conical
seat was fitted a brass plate with a thick rim, but drilled with a
small hole in the centre. To this hole, which was also conical, was
fitted a brass stopper, which could be turned round when the receiver
was exhausted. By attaching a string to this stopper, which was so
long as to enter the receiver to the depth of two or three inches, and
turning the stopper in its seat, the string could be wound up, and
thus objects could be moved within the receiver. The tube at the
bottom of the receiver communicated with a stop-cock, and this with
the upper end of the pumpbarrel, which was inverted, so that this
stop-cock, which was at the top of the barrel, took the place of the
foot-valve. The piston was solid, made of wood, and surrounded with
sole leather, which was kept well greased. There being no valve in the
piston, it was necessary to place an exhaust-valve in the upper end of
the cylinder. This consisted of a small brass plug closing a conical
hole so that it could be removed at pleasure. The construction of the
cylinder was, therefore, similar to that of an ordinary force-pump,
except that the valves had to be moved by hand (as in the early forms
of the steam-engine). The piston was raised and depressed by means of
a rack and pinion. The pumps could be used either for exhausting the
receiver or for forcing air into it, according to the order in which
the "valves" were opened. If the stop-cock communicating with the
receiver were open while the piston was being drawn down, and the
brass plug removed so as to open the exhaust-valve when the piston was
being forced up, the receiver would gradually be exhausted. If the
brass plug were removed during the descent of the piston, and the
stop-cock opened during its ascent, air would be forced into the
receiver. In the latter case it was necessary to take special
precautions to prevent the brass plate at the top of the receiver
being raised from its seat. All joints were made air-tight with
"diachylon," and when, through the bursting of a glass bulb within it,
the receiver became cracked, the crack was rendered air-tight by the
same means. Other receivers of smaller capacity were also provided, on
account of the greater readiness with which they could be exhausted.

With this apparatus Boyle carried out a long series of experiments. He
could reduce the pressure in the large receiver to somewhat less than
that corresponding to an inch of mercury, or about a foot of water.
Squeezing a bladder so as to expel nearly all the air, tying the neck,
and then introducing it into the receiver, he found, on working the
pump, that the bladder swelled so that at length it became completely
distended. In order to account for this great expansibility, Boyle
pictured the constitution of the air in the following way. He supposed
the air to consist of separate particles, each resembling a spiral
spring, which became tightly wound when exposed to great pressure, but
which expanded so as to occupy a larger circle when the pressure was
diminished. Each of these little spirals he supposed to rotate about a
diameter so as to exclude every other body from the sphere in which it
moved. Increasing the length of the diameter tenfold would increase
the volume of one of these spheres, and therefore the volume of the
gas, a thousandfold. Possibly this was only intended as a mental
illustration, exhibiting a mechanism by which very great expansion
might conceivably be produced, and scarcely pretending to be
considered a theory of the constitution of the air. Boyle's first
idea seems to have been derived from a lock of wool in which the
elasticity of each fibre caused the lock to expand after it had been
compressed in the hand. In another passage he speaks of the air as
consisting of a number of bodies capable of striking against a surface
exposed to them. He demonstrated the weight of the air by placing a
delicate balance within the receiver, suspending from one arm a
bladder half filled with water, and balancing it with brass weights.
On exhausting the air, the bladder preponderated, and, by repeating
the experiment with additional weights on the other arm until a
balance was effected in the exhausted receiver, he determined the
amount of the preponderance. In another experiment he compressed air
in a bladder by tying a pack-thread round it, balanced it from one arm
of his balance in the open air; then, pricking the bladder so as to
relieve the pressure, he found that with the escape of the compressed
air the weight diminished.

One of the most important of his experiments with the air-pump was the
following. He placed within the receiver the cistern of a mercurial
barometer, the tube of which was made to pass through the central hole
in the brass plate, from which the stopper had been removed. The space
around the tube was filled up with cement, and the receiver
exhausted. At each stroke of the pump the mercury in the barometer
tube descended, but through successively diminishing distances, until
at length it stood only an inch above the mercury in the cistern. The
experiment was then repeated with a tube four feet long and filled
with water. This constituted the nineteenth experiment referred to
later on. A great many strokes of the pump had to be made before the
water began to descend. At length it fell till the surface in the tube
stood only about a foot above that in the tank. Placing vessels of
ordinary spring-water and of distilled rain-water in the receiver, he
found that, after the exhaustion had reached a certain stage, bubbles
of gas were copiously evolved from the spring-water, but not from the
distilled water. On another occasion he caused warm water to boil by a
few strokes of the pump; and, continuing the exhaustion, the water was
made to boil at intervals until it became only lukewarm. The
experiment was repeated with several volatile liquids. He also noticed
the cloud formed in the receiver when the air was allowed rapidly to
expand; but the mechanical theory of heat had not then made sufficient
progress to enable him to account for the condensation by the loss of
heat due to the work done by the expanding air. The very minute
accuracy of his observations is conspicuous in the descriptions of
most of his experiments. That the air is the usual medium for the
conveyance of sound was shown by suspending a watch by a linen thread
within the receiver. On exhausting the air, the ticking of the watch
ceased to be heard. A pretty experiment consisted in placing a bottle
of a certain fuming liquid within the receiver; on exhausting the air,
the fumes fell over the neck of the bottle and poured over the stand
on which it was placed like a stream of water. Another experiment, the
thirty-second, is worthy of mention on account of the use to which it
was afterwards applied in the controversy respecting the cause of
suction. The receiver, having been exhausted, was removed from the
cylinder, the stop-cock being turned off, and a small brass valve, to
which a scale-pan was attached, was placed just under the aperture of
the tube below the stop-cock. On turning the latter, the stream of air
raised the valve, closing the aperture, and the atmospheric pressure
supported it until a considerable weight had been placed in the
scale-pan. Because the receiver could not be exhausted so thoroughly
as the pump-cylinder, Boyle attempted to measure the pressure of the
air by determining what weight could be supported by the piston. He
found first that a weight of twenty-eight pounds suspended directly
from the piston was sufficient to overcome friction when air was
admitted above the piston. When the access of air to the top of the
piston was prevented, more than one hundred pounds additional weight
was required to draw down the piston. The diameter of the cylinder was
about three inches.

Boyle's style of reasoning is well illustrated by the following from
his paper on "The Spring of the Air:"--

"In the next place, these experiments may teach us what to judge of
the vulgar axiom received for so many ages as an undoubted truth in
the peripatetick schools, that Nature abhors and flieth a vacuum, and
that to such a degree that no human power (to go no higher) is able to
make one in the universe; wherein heaven and earth would change
places, and all its other bodies rather act contrary to their own
nature than suffer it.... It will not easily, then, be intelligibly
made out how hatred or aversation, which is a passion of the soul, can
either for a vacuum or any other object be supposed to be in water, or
such like inanimate body, which cannot be presumed to know when a
vacuum would ensue, if they did not bestir themselves to prevent it;
nor to be so generous as to act contrary to what is most conducive to
their own particular preservation for the public good of the universe.
As much, then, of intelligible and probable truth as is contained in
this metaphorical expression seems to amount but to this--that by the
wise Author of nature (who is justly said to have made all things in
number, weight, and measure) the universe, and the parts of it, are so
contrived that it is hard to make a vacuum in it, as if they
studiously conspired to prevent it. And how far this itself may be
granted deserves to be further considered.

"For, in the next place, our experiments seem to teach that the
supposed aversation of Nature to a vacuum is but accidental, or in
consequence, partly of the weight and fluidity, or, at least,
fluxility of the bodies here below; and partly, and perhaps
principally, of the air, whose restless endeavour to expand itself
every way makes it either rush in itself or compel the interposed
bodies into all spaces where it finds no greater resistance than it
can surmount. And that in those motions which are made ob fugam
vacui (as the common phrase is), bodies act without such generosity
and consideration as is wont to be ascribed to them, is apparent
enough in our thirty-second experiment, where the torrent of air, that
seemed to strive to get into the emptied receiver, did plainly prevent
its own design, by so impelling the valve as to make it shut the only
orifice the air was to get [in] at. And if afterwards either Nature or
the internal air had a design the external air should be attracted,
they seemed to prosecute it very unwisely by continuing to suck the
valve so strongly, when they found that by that suction the valve
itself could not be drawn in; whereas, by forbearing to suck, the
valve would, by its own weight, have fallen down and suffered the
excluded air to return freely, and to fill again the exhausted

"And as for the care of the public good of the universe ascribed to
dead and stupid bodies, we shall only demand why, in our nineteenth
experiment, upon the exsuction of the ambient air, the water deserted
the upper half of the glass tube, and did not ascend to fill it up
till the external air was let in upon it. Whereas, by its easy and
sudden rejoining that upper part of the tube, it appeared both that
there was then much space devoid of air, and that the water might,
with small or no resistance, have ascended into it, if it could have
done so without the impulsion of the readmitted air; which, it seems,
was necessary to mind the water of its formerly neglected duty to the

Boyle then goes on to explain the phenomena correctly by the pressure
of the air. Elsewhere he accounts for the diminished pressure on the
top of a mountain by the diminished weight of the superincumbent
column of air.

The treatise on "The Spring of the Air" met with much opposition, and
Boyle considered it necessary to defend his doctrine against the
objections of Franciscus Linus and Hobbes. In this defence he
described the experiment in connection with which he is most generally
remembered. Linus had admitted that the air might possess a certain
small amount of elasticity, but maintained that the force with which
mercury rose in a barometer tube was due mainly to a totally different
action, as though a string were pulling upon it from above. This was
his funicular hypothesis. Boyle undertook to show that the pressure of
the air might be made to support a much higher column of mercury than
that of the barometer. To this end he took a glass tube several feet
in length, and bent so as to form two vertical legs connected below.
The shorter leg was little more than a foot long, and hermetically
closed at the top. The longer leg was nearly eight feet in length, and
open at the top. The tube was suspended by strings upon the staircase,
the bend at the bottom pressing lightly against the bottom of a box
placed to receive the mercury employed in case of accident. Each leg
of the tube was provided with a paper scale. Mercury was poured in at
the open end, the tube being tilted so as to allow some of the air to
escape from the shorter limb until the mercury stood at the same level
in both legs when the tube was vertical. The length of the closed tube
occupied by the air was then just twelve inches. The height of the
barometer was about 29-1/8 inches. Mercury was gently poured into the
open limb by one operator, while another watched its height in the
closed limb. The results of the experiments are given in the table on
the opposite page.

In this table the third column gives the result of adding to the
second column the height of the barometer, which expresses in inches
of mercury the pressure of the air on the free surface of the mercury
in the longer limb. The fourth column gives the total pressure, in
inches of mercury, on the hypothesis that the pressure of the air
varies inversely as the volume. The agreement between the third and
fourth columns is very close, considering the roughness of the
experiment and that no trouble appears to have been taken to
calibrate the shorter limb of the tube, and justified Boyle in
concluding that the hypothesis referred to expresses the relation
between the volume and pressure of a given mass of air.

Length of Height of Total pressure Total pressure
closed tubemercury in openon air in inchesaccording to
occupied tube above thatof mercury. Boyle's law.
by air. in closed tube.
12 0 29-2/16 29-2/16
11-1/2 1-7/16 30-9/16 30-6/16
11 2-13/16 31-15/16 31-12/16
10-1/2 4-6/16 33-8/16 33-1/7
10 6-3/16 35-5/16 35
9-1/2 7-14/16 37 36-15/19
9 10-1/16 39-3/16 38-7/8
8-1/2 12-8/16 41-10/16 41-2/17
8 15-1/16 44-3/16 43-11/16
7-1/2 17-15/16 47-1/16 46-3/5
7 21-3/16 50-5/16 50
6-1/2 25-3/16 54-5/16 53-10/13
6 29-11/16 58-13/16 58-2/8
5-3/4 32-3/16 61-5/16 60-13/23
5-1/2 34-15/16 64-1/16 63-6/11
5-1/4 37-15/16 67-1/16 66-4/7
5 41-9/16 70-11/16 70
4-3/4 45 74-2/16 73-11/19
4-1/2 48-12/16 77-14/16 77-2/3
4-1/4 53-11/16 82-13/16 82-4/17
4 58-2/16 87-14/16 87-1/8
3-3/4 63-15/16 93-1/16 93-1/5
3-1/2 71-5/16 100-7/16 99-6/7
3-1/4 78-11/16 107-13/16 107-7/13
3 88-7/16 117-9/16 116-4/8

To extend the investigation so as to include expansion below
atmospheric pressure, a different apparatus was employed. It consisted
of a glass tube about six feet in length, closed at the lower end and
filled with mercury. Into this bath of mercury was plunged a length of
quill tube, and the upper end was sealed with wax. When the wax and
air in the tube had cooled, a hot pin was passed through the wax,
making a small orifice by which the amount of air in the tube was
adjusted so as to occupy exactly one inch of its length as measured by
a paper scale attached thereto, after again sealing the wax. The quill
tube was then raised, and the height of the surface of the mercury in
the tube above that in the bath noticed, together with the length of
the tube occupied by the air. The difference between the height of the
barometer and the height of the mercury in the tube above that in the
bath gave the pressure on the imprisoned air in inches of mercury. The
result showed that the volume varied very nearly in the inverse ratio
of the pressure. A certain amount of air, however, clung to the sides
of the quill tube when immersed in the mercury, and no care was taken
to remove it by boiling the mercury or otherwise; in consequence of
this, as the mercury descended, this air escaped and joined the rest
of the air in the tube. This made the pressure rather greater than it
should have been towards the end of the experiment, and when the tube
was again pressed down into the bath it was found that, when the
surfaces of the mercury within and without the tube were at the same
level, the air occupied nearly 1-1/8 inch instead of one inch of the
tube. These experiments first established the truth of the great law
known as "Boyle's law," which states that the volume of a given mass
of a perfect gas varies inversely as the pressure to which it is

Another experiment, to show that the pressure of the air was the cause
of suction, Boyle succeeded in carrying out at a later date. Two discs
of marble were carefully polished, so that when a little spirit of
turpentine was placed between them the lower disc, with a pound weight
suspended from it, was supported by the upper one. The apparatus was
introduced into the air-pump, and a considerable amount of shaking
proved insufficient to separate the discs. After sixteen strokes of
the pump, on opening the communication between the receiver and
cylinder, when no mechanical vibration occurred, the discs separated.

Upon the Restoration in 1660, the Earl of Clarendon, who was Lord
Chancellor of England, endeavoured to persuade Boyle to enter holy
orders, urging the interest of the Church as the chief motive for the
proceeding. This made some impression upon Boyle, but he declined for
two reasons--first, because he thought that he would have a greater
influence for good if he had no share in the patrimony of the Church;
and next, because he had never felt "an inward motion to it by the
Holy Ghost."

In 1649 an association was incorporated by Parliament, to be called
"the President and Society for the Propagation of the Gospel in New
England," whose object should be "to receive and dispose of moneys in
such manner as shall best and principally conduce to the preaching and
propagating the gospel among the natives, and for the maintenance of
schools and nurseries of learning for the education of the children of
the natives; for which purpose a general collection was appointed to
be made in and through all the counties, cities, towns, and parishes
of England and Wales, for a charitable contribution, to be as the
foundation of so pious and great an undertaking." The society was
revived by special charter in 1661, and Boyle was appointed president,
an office he continued to hold until shortly before his death. The
society afterwards enlarged its sphere of operations, and became the
Society for the Propagation of the Gospel in Foreign Parts.

In the same year (1661) Boyle published "Some Considerations on the
Usefulness of Experimental Natural Philosophy," etc., and in 1663 an
extremely interesting paper on "Experiments and Considerations
touching Colours." In the course of this paper he describes some very
beautiful experiments with a tincture of Lignum nephriticum, wherein
the dichroism of the extract is made apparent. Boyle found that by
transmitted light it appeared of a bright golden colour, but when
viewed from the side from which it was illuminated the light emitted
was sky blue, and in some cases bright green. By arranging experiments
so that some parts of the liquid were seen by the transmitted light
and some by the scattered light, very beautiful effects were produced.
Boyle endeavoured to learn something of the nature of colours by
projecting spectra on differently coloured papers, and observing the
appearance of the papers when illuminated by the several spectral
rays. He also passed sunlight, concentrated by a lens, through plates
of differently coloured glass superposed, allowing the light to fall
on a white paper screen, and observing the tint of the light which
passed through each combination. But the most interesting of these
experiments was the actual mixture of light of different colours by
forming two spectra, one by means of a fixed prism, the other by a
prism held in the hand, and superposing the latter on the former so
that different colours were made to coincide. This experiment was
repeated in a modified form, nearly two hundred years later, by
Helmholtz, who found that the mixture of blue and yellow lights
produced pink. Unfortunately, Boyle's spectra were far from pure, for,
the source of light being of considerable dimensions, the different
colours overlapped one another, as in Newton's experiments, and in
consequence some of his conclusions were inaccurate. Thus blue paper
in the yellow part of the spectrum appeared to Boyle green instead of
black, but this was due to the admixture of green light with the
yellow. He concluded that bodies appear black because they damp the
light so as to reflect very little to the eye, but that the surfaces
of white bodies consist of innumerable little facets which reflect the
light in all directions. In the same year he published some
"Observations on a Diamond, which shines in the Dark;" and an
extensive treatise on "Some Considerations touching the Style of the
Holy Scriptures." Next year appeared several papers from his pen, the
most important being "Occasional Reflections upon Several Subjects,"
the wide scope of which may be gathered from the title. His "New
Experiments and Observations touching Cold" were printed in 1665. In
this paper he discussed the cause of the force exerted by water in
freezing, methods of measuring degrees of cold, the action of
freezing-mixtures, and many other questions. He contended that cold
was probably only privative, and not a positive existence.

Lord Bacon had asserted that the "essential self" of heat was probably
motion and nothing more, and had adduced several experiments and
observations in support of this opinion. In his paper on the
mechanical origin of heat and cold, Boyle maintained that heat was
motion, but motion of the very small particles of bodies, very
intense, and taking place in all directions; and that heat could be
produced by any means whatever by which the particles of bodies could
be agitated. On one occasion he caused two pieces of brass, one convex
and the other concave, to be pressed against each other by a spring,
and then rubbed together in a vacuum by a rotary motion communicated
by a shaft which passed air-tight through the hole in the cover of the
receiver, a little emery being inserted between them. In the second
experiment the brasses became so hot that he "could not endure to hold
[his] hand on either of them." This experiment was intended, like the
rubbing of the blocks of ice in vacuo by Davy, to meet the objection
that the heat developed by friction was due to the action of the air.
The following extract from a paper intended to show that the sense of
touch cannot be relied upon for the estimation of temperature, shows
that Boyle possessed a very clear insight into the question:--"The
account upon which we judge a body to be cold seems to be that we feel
its particles less vehemently agitated than those of our fingers or
other parts of the organ of touching; and, consequently, if the temper
of that organ be changed, the object will appear more or less cold to
us, though itself continue of one and the same temperature." To
determine the expansion of water in freezing, he filled the bulb and
part of the stem of a "bulb tube," or, as it was then generally
called, "a philosophical egg," with water, and applying a
freezing-mixture, at first to the bottom of the bulb, he succeeded in
freezing the water without injury to the glass, and found that 82
volumes of water expanded to 91-1/8 volumes of ice--an expansion of
about 11-1/8 per cent. Probably air-bubbles caused the ice to appear
to have a greater volume than it really possessed, the true expansion
being about nine per cent. of the volume of the water at 4 deg.C. The
expansion of water in freezing he employed in order to compress air to
a greater extent than he had been able otherwise to compress it.
Having nearly filled a tube with water, but left a little air above,
and then having sealed the top of the tube, he froze the water from
the bottom upwards, so that in expanding it compressed the air to
one-tenth of its former volume.

Magnetism and electricity came in for some share of Boyle's attention.
He carried out a number of experiments on magnetic induction, and
found that lodestones, as well as pieces of iron, when heated and
allowed to cool, became magnetized by the induction of the earth. His
later experiments with exhausted receivers were not made with his
first pump, but with a two-barrelled pump, in which the pistons were
connected by a cord passing over a large fixed pulley, so that, when
the receiver was nearly exhausted, the pressure of the air on the
descending piston during the greater part of the stroke nearly
balanced that on the ascending piston. In this respect the pump
differed only from Hawksbee's in having the pulley and cord instead of
the pinion and two racks. It also resembled Hawksbee's pump in having
self-closing valves in the pistons and at the bottom of the cylinders,
which, in this pump, had their open ends at the top. The pistons were
alternately raised and lowered by the feet of the operator, which were
placed in stirrups, of which one was fixed on each piston. The lower
portions of the barrels were filled with water, through which the air
bubbled, and this, occupying the clearance, enabled a much higher
degree of exhaustion to be produced than could be obtained without its

In 1665 Boyle was nominated Provost of Eton, but declined to accept
the appointment. His "Hydrostatical Paradoxes," published about this
time, contain all the ordinary theorems respecting the pressure of
fluids under the action of gravity demonstrated experimentally.

In 1677 Boyle printed, at his own expense, five hundred copies of the
four Gospels and the Acts of the Apostles in the Malayan tongue. This
was but one of his many contributions towards similar objects.

On November 30, 1680, the Royal Society chose Boyle for President. He,
however, declined to accept the appointment, because he had
conscientious objections to taking the oath required of the President
by the charter of the Society.

It appears that very many of Boyle's manuscripts, which were written
in bound books, were taken away, and others mutilated by "corrosive
liquors." In May, 1688, he made this known to his friends, but, though
these losses put him on his guard, he complained afterwards that all
his care and circumspection had not prevented the loss of "six
centuries of matters of fact in one parcel," besides many other
smaller papers. His works, however, which have been published are so
numerous that it would take several pages for the bare enumeration of
their titles, many of them being devoted to medical subjects. The
edition published in London in 1743 comprises nearly three thousand
pages of folio. Boyle always suffered from weak eyes, and in
consequence he declined to revise his proofs. In the advertisement to
the original edition of his works the publisher mentioned this, and at
the same time pleaded his own business engagements as an excuse for
not revising the proofs himself! It was partly on account of the
injury to his manuscripts, and partly through failing health, that in
1689 he set apart two days in the week, during which he declined to
receive visitors, that he might devote himself to his work, and
especially to the reparation of the injured writings. About this time
he succeeded in procuring the repeal of an Act passed in the fifth
year of Henry IV. to the effect "that none from thenceforth should use
to multiply gold or silver, or use the craft of multiplication; and if
any the same do, they should incur the pain of felony." By this repeal
it was made legal to extract gold and silver from ores, or from their
mixtures with other metals, in this country provided that the gold and
silver so procured should be put to no other use than "the increase of
moneys." It is curious that Boyle seems always to have believed in the
possibility of transmuting other metals into gold.

His sister, Lady Ranelagh, died on December 23, 1691, and Boyle
survived her but a few days, for he died on December 30, and his body
was interred near his sister's grave in the chancel of St.
Martin's-in-the-Fields. Dr. Shaw, in his preface to Boyle's works,
writes, "The men of wit and learning have, in all ages, busied
themselves in explaining nature by words; but it is Mr. Boyle alone
who has wholly laid himself out in showing philosophy in action. The
single point he perpetually keeps in view is to render his reader, not
a talkative or a speculative, but an actual and practical philosopher.
Himself sets the example; he made all the experiments he possibly
could upon natural bodies, and communicated them with all desirable
candour and fidelity." The second part of his treatise on "The
Christian Virtuoso," Boyle concluded with a number of aphorisms, of
which the following well represent his views respecting science:--

"I think it becomes Christian philosophers rather to try whether they
can investigate the final causes of things than, without trial, to
take it for granted that they are undiscoverable."

"The book of Nature is a fine and large piece of tapestry rolled up,
which we are not able to see all at once, but must be content to wait
for the discovery of its beauty and symmetry, little by little, as it
gradually comes to be more unfolded or displayed."

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