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and in this state of the disease the testicle can matic vessels. The contents of the tumor being not be felt without much difficulty. On a ininute discharged, the sore is to be treated like any other examination, a hardness is always to be felt simple wound. along that part of the scrotum where the testicle Encysted hydrocele of the spermatic corni is situated'; and at this point pressure excites sometimes begins in the upper, but generally is some uneasiness. Fluctuation of fluid may in the lower part of the spermatic cord. On its general be distinguished through the whole course first appearance it is so small as to give little or of the disease. In late stages, however, the ap no trouble; hence it is seldom particularly atpearance of a fluid is not very evident.
tended to till it has acquired a considerable size. The transparency of the tumor has been gene- By degrees it extends as far as the abdominal rally supposed to be the principal criterion of muscles, and sometimes reaches to the bottom this species of the disorder: but this must de- of the scrotum; and, to a person unacquainted pend upon the nature of the contents, or thick- with the appearance of the disorder, may be ness of the sac; so that, though the transparency mistaken for a hydrocele of the tunica vaginalis. of the tumor is a certain sign of the exisience of But here the tumor is always above the testicle, water, its opacity cannot upon any account be which is distinctly felt below; whereas, in the considered as an indication of its absence. advanced stages of hydrocele in the vaginal coat Through the whole course of the disease, the the testicle cannot be distinctly felt. tumor is not attended with pain, but some un- cysted hydrocele of the cord, the figure and size easiness is commonly felt in the back by the of the penis is little altered ; whereas, in cases weight of the swelling of the spermatic cord. of common hydrocele, the penis frequently disThis is more particularly the case when a sus- appears almost entirely. In adults, the cyst, in pensory bandage is not used. In the radical every variety of incysted hydrocele, becomes so cure of hydrocele, in whatever way it is attempt- firm as not to be affected by external applicaed, some degree of inflammation will take place. tions; so that, when the tumor becomes large, it
The cure of the hydrocele of the tunica was is necessary to use means for producing either a formerly effected by one of three methods; either palliative or radical cnre, in the same manner as by caustic, by the seton, or by, incision. Al- is done for a hydrocele in the tunica vaginalis. though in most cases any one of these methods See SURGERY and Medicine. will induce a cure, yet that of simple incision is HYDROCEPHALUS, in medicine, (frons less liable to produce violent inflammation, the vowp water, and sepakn the head), is as the name danger of which from the proximity of the in- imports a dropsy of the head, and is commonly testines is too evident to require discussion. called water on the brain. It is a disease almost
But the surgeons of the present day do not peculiar to children, being seldom observed in generally make use of any of these systems. persons above the age of twelve or fourteen, and The cure is now generally attempted by the in- it seems to be most prevalent in scrofulous jection of some irritating fluid which will cause families. With respect to the proximate cause infiammation throughout the whole extent of the of hydrocephalus very opposite opinions are tunica. The preference is usually given to wine, entertained by different medical writers. It and commonly that is somewhat diluted ; but, appears generally to begin with slight inflamwhere no pain is excited by the injection, the mation, but whether as a cause or only as a liquor should be discharged, and a stronger one symptom is a matter of dispute. The disease used. For where no pain takes place a cure is appears to be constitutional. Patients usually not to be expected.
complain first of a pain in some part below the The hydrocele of the spermatic cord is either head, commonly about the nape of the neck and anasarcous or encysted. The anasarcous kind shoulders; often in the legs; and sometimes, but is attended with a colorless tumor in the course rarely, in the arms. The pain is not uniformly of the spermatic curd, soft and inelastic to the acute, nor always fixed to one place; and some touch, and unaccompanied with fluctuation. In times does not affect the limbs. Some have violent an erect position of the body it is of an oblong sickness and head-aches alternately. From being figure; but, when the body is recumbent, it is perfectly well and sportive, some are in a few flatter. Generally it is no longer than that part hours seized with those pains in the limbs, or of the cord which lies in the groin, though it with sickness, or head-ach, in a slight degree ; sometimes extends as far as the testicle, and even whilst others are observed to droop a few days stretches the scrotum to an uncommon size; an before they complain of any local indisposition. instance of which is related by Mr. Pott, who In this manner they continue three, four, or five from a swelling of this kind discharged eleven days. They then complain of an acute deeppints at once. By pressure a great part of the seated pain in the head, extending across the swelling can always be made io recede into the forehead from temple to temple; of which, and abdomen'; but it instantly returns to its former a sickness, they alternately complain in short situation on the pressure being withdrawn. and affecting exclamations; dosing a little in the
When the tumor is connected with general intervals, breathing irregularly, and sighing much anasarea of the system, it can only be cured with while awake. Sometimes their sighs, for a few the rest of the disease; but, when the swelling is minutes, are incessant. As the disease advances, local, the remedy is also to be locally applied. the pulse becomes slower and irregular, till An incision is to be made of such a size as may within a day or two of the fatal termination, be sufficient for discharging the whole of the when it becomes exceedingly quick; the breathwater; in the performance of which, attention ing being deep, irregular, and laborious. After is necessary to guard against hurting the sper- the first access, which is often attended wit's
feverish heats, the heat of the body is for the the Journal of Science, states, that carbonic most part temperate, till at last it keeps pace oxide produces, by the action of its flame, simiwith the increasing quickness of the pulse. "The lar sounds, and that therefore the effect is nog head and præcordia are always hot from the first due to the affections of aqueous vapor, as bad attack. The sleeps are short and disturbed, some formerly' been supposed. He shows, that the times interrupted by watchfulness and startings. sound is nothing more than the report of a conIn the first stage there is a peculiar sensibility tinued explosion, agreeably to Sir H. Davy's of the eyes, and intolerance of light. But in theory of the constitution of fame. Vapor of the progress of the disease a very opposite state' ether, made to burn from a small aperture, prouccurs. The pupil is remarkably dilated, and duces the same sonorous effect as the jet of hy. cannot he made to contract by the action even drogen, of coal gas, or olefiant gas, on glass and of strong light. Various methods of cure have other tubes. Globes from seven to two inches been attempted, but the disease almost always in diameter, with short necks, give very low terminates fatally. See MediciŅE.
tones; bottles, Florence flasks, and phials, always HYDROCYANIC Acro. See Prussic succeeded; air jars, from four inches diameter Acıp. HYDROCHARIS, the little water lily, a
to a very small size, may be used. Some angular
tubes were constructed of long narrow slips of genus of the enneandria order, and diccia class glass and wood, placing three or four together, of plants: natural order first, palmæ. Male so as to form a triangular or square tube, tying spatha diphyllous: cal. trifid : cor. tripetalous; them round with pack-thread. These, held over the three inferior filaments styliferous.' Female the hydrogen jet, gave distinct tones. CAL. trifid : cor. tripetalous; the styles six : Professor Dobereiner has discovered that, by caps. six celled and polyspermous inferior. throwing a jet of hydrogen yas on a small pellet There is only one species, a native of Britain, of spongy platinum, the platinum instantly begrowing in slow streams and wet ditches. It comes red hot and the jet of hydrogen inflamed. has kidney-shaped leaves, thick, smooth, and of Mr. Gordon of Oxford Street has formed a lamp a brownish-green color, with white blossoms. on this principle, which is actually a Rew appaThere is a variety with double flowers of a very ratus for procuring instantaneous fire. See our sweet smell.
articles CHEMISTRY in which the nature properHYDROCOTYLE, water navelwort, a genus ties and combination of hydrogen are fully of the digynia order, and pentandria class of treated uf, and Gas in which its application to plants; natural order forty-fifth, umbellatæ. The lighting of roads, shops, &c., is detailed. One umbel is simple; the involucrum tetraphyllous; of the principal objections to its use as a light the petals entire; the seeds are half round and is the strong disagreeable smell. But if hydrocompressed. There are several species, none of gen gas, obtained by the solution of iron in sulwhich are ever cultivated in gardens. One of phuric acid, be made to pass into pure alcohol, them, a native of Britain, growing in marshy it almost entirely loses its smell. Water addel grounds, is supposed by some farmers to occa to the alcohol renders it milky; and, on resting sion the rot in sheep. The leaves have central some hours, a volatile oil separates, which is the leaf-stalks, with about five flowers in a rundle; cause of the well-known smell of hydrogen gas. the petals are of a reddish white.
This gas is obtained perfectly free of smell, by HYDROGEN Gas, in chemistry (from vowp, putting into pure water an amalgam of potassium; water and yevvaw to produce), is the lightest but, if there be added to the water an acid or species of ponderable matter hitherto discovered. sal-ammoniac to accelerate the development of The following is the best method of obtaining the gas, the latter will have the smell, which is it :-Into a phial furnished with a bent tube fitted observed during the solution of zinc in weak to its cork, or into a retort, put some pieces of sulphuric acid. Ann. de Chim. et de Phys., pure redistilled zinc, or harpsichord iron wire, October 1824. and pour on them sulphuric acid diluted with
HYDROGʻRAPHER, n. s. ? Fr. hydrofive times its bulk of water. An effervescence
HYDROGRAPHY, n. s.
Igraphe; Greek, will ensue, occasioned by the decomposition of the water, and disengagement of 'hydrogen, sea. Description of the watery parts of the
υδωρ and γραφω.
One who draws maps of the which may be collected in the pneumatic apparatus. For very accurate researches, it must be
globe. received in jars over mercury, and exposed to
It may be drawn from the writings of our hydrothe joint action of dry muriate of lime, and a graphers.
Boyle. low temperature. It derived its name from the HYDROGRAPHY is the art of measuring and property it possseses of forming water when describing the sea, rivers, canals, lakes, &c. mixed with oxygen, and exposed to the electric With regard to the sea, it gives an account of shock. If a bottle, containing the effervescing its tides, counter-tides, soundings, bays, gulfs, mixture of iron and dilute sulphuric acid, be creeks, &c.; also the rocks, shelves, sands, shalshul with a cork, having a straight tube of nar. .dows, promontories, harbours; the distance and row bore fixed upright in it, then the hydrogen bearing of one port from another; with every will issue in a jet, which, being kindled, forms thing that is remarkable, whether out at sea or the philosophical candle of Dr. Priestley. If a on the coast. long glass tube be held over the flame, moisture HYDROLEA, in botany, a genus of the diwill speedily bedew its sides, and harmonic tones gynia order, pentandria class of plants: CAL. will soon begin to sound. Mr. Faraday, in an pentaphyllous: cor. rotaceous ; the filaments at ingenious paper inserted in the tenth number of ine base cordate: caps. bilocular and bivalved.
There are four species, two of which are natives ness, or even throw the patient into convulsions. of South America, two of the East Indies. The patient, however, is not as yet deprived of
HY'DROMANCY, n. s. Fr. hydromuntie ; reason. Some have, merely by the dini of resoGr. ύδωρ and μαντία. Prediction by water. lution, conquered the dread of water, though
Divination was invented by the Persians : there are they never could overcome the convulsive mofour kinds of divination ; hydromancy, pyromancy, tions wbich the contact of liquids occasioned, aeromancy, and geomancy.
Ayliffe. and yet this has been of no avail; for the convulHY'DROMEL, n. s. Fr. hydromel; Gr. sions and other symptoms increasing, have always ööwp and péd. Honey and water.
overpowered the individual at last; and a great Hydromel is a drink prepared of honey, being one
flow of viscid saliva into the mouth now takes of the most pleasant and universal drinks the northern place; as it has the same effect upon their fauces part of Europe affords, as well as one of the most that other liquids have. This therefore is blown ancient.
Mortimer. off with violence, which in a patient of Dr. FoIn fevers the aliments prescribed by Hippocrates thergill's occasioned a noise like the barking of were ptisans and cream of barley : hydromel, that is, a dog. Patients then have an insatiable thirst, honey and water, when there was no tendency to a but are unable to get down any drink without delirium.
the utmost difficulty; though sometimes they HYDROM'ETER, n.s. ? Greek, vèwp and can swallow bread soaked in. liquids, slices of HYDROM'ETRY, n. S. S
μέτρον. An instru- oranges, or other fruits. There is a pain under ment to measure the extent or depth of water: the scrobiculus cordis, as in the tetanus. But the act of measuring it.
the symptoms are so various, that they cannot HYDROPHOʻBIA, n. s. Fr. hydrophobie ; be enumerated; for we seldom read two cases of Gr. vèpopoßia. Dread of water.
hydrophobia which do not differ very remarkably. Hydrophobia is a kind of madness, well known in Sometimes every member is convulsed by fits, every village, which comes by the biting of a mad but most violently from the navel up to the breast dog; or scratching [saith Aurelianus), touching, or and esophagus. • The fit comes on perhaps smelling alone, sometimes (as Sckenkins proves), every quarter of an hour, the fauces are not red, and is incident to many other creatures as well as nor the tongue dry. The pulse is not at all feman; so called because the parties so affected cannot verish; and, when the fit is over, nearly like a en:lure the sight of water, or any liquor, supposing sound pulse. The face grows, pale, then brown, still they see a mad dog in it. Burton. Anat. Mel.
and during the fit almost black, the lips livid, the HYDROPHOBIA in medicine, is a disease gene- head is drowsy, and the ears tingling; the urine rally communicated to man by the bite of a limpid. At last the patient is weary, the fits are rabid dog, and is so called because one of its prin- less violent, the pulse becomes weak, intermittent, cipal symptoms is the inability of the patient to and not very quick ; and at last the whole body swallow water or any other liquid. It is called becomes cold. If the patient can get sleep, so by some writers canine madness, and seldom he will expire. The blood drawn a few hours makes its appearance till a considerable time before death appears good in every respect. The after the bite of the rabid animal. In some few hydrophobia seems to be a symptom peculiar to instances it has commenced in seven or eight the human race; for the mad animals which days from the accident; but generally the patient communicate the infection do not seem to have continues in health for twenty, thirty, or forty any dread of water. days, or even much longer. The bite will in With regard to the symptoms of madness in general be healed long before that time, frequent- dogs, they are very equivocal; and those partily with the greatest ease ; though sometimes it cularly enumerated by some authors are only resists all kinds of healing applications, and such as might be expected in dogs much heated forms a running ulcer, which discharges a quan- or agitated by being violently pursued and struck. tity of matter for many days. The approach of The most certain symptom, indeed, is that all the disease is known by the cicatrix of the wound other dogs avoid and run away from one that is becoming high, hard, and elevated, and by a mad; and even large dogs will not attack one of peculiar sense of prickling at the part; pains the smallest size who is infected with this disshoot from it towards the throat; sometimes it ease. You may discover whether a dog who is surrounded with livid or red streaks, and has been killed was really mad or not, by rubseems to be in a state of inflammation; though bing a piece of meat along the inside of his often there is nothing remarkable to be observed. mouth, and then offering it to a sound dog. If The patient becomes melancholy, loves solitude, the latter eats it, it is a sign the dog was not mad; and feels sickness at the stomach. Sometimes but, if the other rejects it with a kind of a how:the peculiar symptom, the dread of water, comes ing noise, it is certain that he was. Dr. James on all at once. Sometimes the disease begins like tel!s us, that among dogs the disease is infectious a common sore throat; and, the soreness daily by staying in the same place; and, that after a increasing, the hydrophobic symptoms appear kennel has been once infected, the dogs put into like a convulsive spasm of the muscles of the it will be for a considerable time afterwards in fauces. In others, the mind is first affected, and danger of going mad. He rejects as false the a real dread of water arises before the patient opinion, that dogs, when going mad, will not tries whether he can swallow it. But, in what- bark: though he owns that there is a very consiever manner this symptom comes on, the most derable change in their bark which becomes painful sensations accompany every attempt to hoarse and hollow. swallow liquids. Nay, the bare sight of water, It is said, that the causes commonly assigned or any thing clear, will give the utmost ureasi- for this disease among animals viz. heat, feeding
upon putrid Aesh, want of water, &c., are not longitudinal stria on the inside; the stigma is sufficient to produce the distemper. It does not bifid : CAPS. globose and bivalved. There are appear that madness is more frequent among three species, the chief is-H, Virginianum, the dogs in the warm than in the cold climates; water leaf of Morinus. It grows naturally in nay, in the island of Antigua, where the Canada and many other parts of America on climate is very hot, and the water very scarce, moist spongy ground. The root is composed of. this distemper has never, it is said, been observ- many strong fleshy fibres, from which arise many ed. As to putrid aliment, it seems natural for leaves with foot-stalks five or six inches long, dogs to prefer this to any other, and they have jagged into three, five, or seven lobes, almost to been known to subsist upon it for a long time the mid-rib, indented on their edges. The flowers, without detriment. With regard to the imme- are produced in loose clusters hanging dowodiate cause among mankind, there is not the wards, are bell-shaped, and of a dirty white least doubt that the hydrophobia is occasioned color. It may be propagated by parting the by the saliva of the mad animal being mixed roots; which ought to be done in autumn, that with the blood. It does not appear that this the plants may be well rooted before spring, can operate through the cuticula; but, when that otherwise they will require a great deal of water. is rubbed off, the smallest quantity is sufficient
HYDROPICAL, adj. ?
} from Lat. hydrops
, to communicate the disease, and a slight scratch HydroPiCK, adj. with the teeth of a mad animal has been found Gr. vòpo nikóg. Dropsical; diseased with extraas pernicious as a large wound. It is certain, vasated water : resembling dropsy. also, that the infection has been communicated Cantharides heat the watery parts of the body; as by the bites of dogs, cats, wolves, foxes, weasels, urine, and hydropical water. swine, and even cocks and hens, when in a state
Bacon's Natural History. of madness.
The world's whole sap is sunk : If the disease once exhibits its symptoms in a The general balm the hydropick earta hath drunk.
Donne. human patient the chances , for recovery are small indeed : there having never been one well
Every lust is a kind of hydropick distemper, and the
more we drink the more we shall thirst. Tillotson. authenticated case of the recovery of a really
Hydropick wretches by degrees decay, hydrophobous person.-Prevention is the only
Growing the more, the more they waste away; chance, and removal of the contagious matter the
By their own ruins they augmented lye, only fair hope, of preserving life. Of all the With thirst and heat amidst a deluge fry. means of removal, the cutting out the part to
Blackmore. which the tooth has been applied, is unquestion, Hydropical swellings, if they be pure, are pellucid. ably the most effectual. This therefore should
Wiseman. not be delayed ; one-quarter of 'an hour's One sort of remedy he uses in dropsies, the water hesitation will sometimes prove fatal. But, be- of the hydropicks.
Arbuthnot. sides cutting away the part, careful washing may HYDROSELENIC Acid. The best process be used. Cold water should be poured upon the which we can employ for procuring this acid, acwound from a considerable height, that the mat- cording to M. Berzelius, consists in treating the ter may be washed away with some force. Even seleniuret of iron with the liquid muriatic acid. after removal by the kpife careful washing is The acid gas evolved must be collected over still proper. And after both these, to prevent, mercury. As in this case a little of another gas, as far as can be, the possibility of any contagious condensable neither by water nor alkaline solumatter lurking about the wounded part, it should tions, appears, the best 'substance for obtaining not be allowed to heal, but a discharge of matter absolutely pure hydroselenic acid would be seshould be supported for several weeks, by oint- leniuret of potassium. ment with cantharides, or similar applications. Seleniureted hydrogen gas is colorless. It By these means there is the best chance of re- reddens litmus. Its density has not been determoving the matter at a sufficiently early period. mined by experiment. Its smell resembles, at Prevention may also be obtained by the destruc- first, that of sulphureted hydrogen gas; but the tion of the contagious matter at the part; and, sensation soon changes, and another succeeds, where there is the least reason to think that a which is at once pungent, astringent, and paincomplete removal has not been obtained, these ful. The eyes become almost instantly red and should always be had recourse to. With this inflamed, and the sense of smelling entirely intention the actual cautery, and burning with disappears. A bubble of the size of a little pea gun-powder, have been employed. And fire is, is sufficient to produce these effects. Of all the doubtless, one of the most powerful agents that bodies derived from the inorganic kingdom, secan be used for this purpose. Recourse has also leniureted hydrogen is that which exercises the been had to washing, both with acids and alka- strongest action on the animal economy. Water lies. Of the former, vinegar has been chiefly dissolves this gas; but in what proportions is not used; but more may be expected from the latter, known. This solution disturbs almost all the particularly from the caustic alkali, so far dilu- metallic solutions, producing black or brown ted that it can be applied with safety; for, from precipitates, which assume, on rubbing with its influence as a solvent of animal mucus, it polished hæmatites, a metallic lustre. Zinc, gives a better chance of a complete removal of manganese, and cerium, form exceptions. They the poison. See MEDICINE, Index.
yield fesh-colored precipitates, which appear to HYDROPHYLUM, water leaf : a genus of be hydro-seleniurets of the oxides, whilst the the monogynia order, and pentandria class of others, for the most part, are merely métallic seplants : COR. campanulated, with five melliferous leniềrets.
HYDROSTATICS AND HYDRAULICS.
HYDROSTAT’ICAL, adj. Gr. vowp and entirely conclusive, because they had no means HYDROSTATICALLY, adv.
The of determining whether the diminution of the HYDROSTAT'ics, n. S. science of weigh- internal capacity of the globe by pressure, was ing fluids, and bodies in fluids.
exactly equal to the quantity of water forced A buman body forming in such a Quid, will never through its pores; but they certainly proved the be reconciled to this hydrostatical law; there will be extreme minuteness of the particles that could always something lighter beneath, and something be forced through so dense a metal as gold. heavier above; because bone, the heaviest in specie, The inference, drawn by the Florentines, rewill be ever in the midst.
Bentley. mained uncontradicted till about 1762, when The weight of all bodies around the earth is ever Canton published some experiments on the proportional to the quantity of their matter : for in- subject. 'With the barometer at 29}', and the stance, a pound weight, examined hydrostatically, doth thermometer at 50°, he states the following to be always contain an equal quantity of solid mass. ld.
the results obtained :HYDROSTATICs and HYDRAULICS; from vowp, water, and sarun, the art of weighing: and Compression of spirits
of wine jowp and avlos, a pipe or flute, (the doctrine of
66 parts in 1,000,000 . Oil of olives
48 Ditto machines worked by water, because organs when
46 Ditto first invented were thus first sounded, or filled
40 Ditto with wind). In the arrangement of our more important treatises we endeavour to unite the
Mercury consideration of scientific propriety with the con These results he obtained in the following venience of alphabetical order. Looking only to manner: he took a glass tube, about two feet the latter of these, in regard to the above sciences, long, with a ball at one end, of an 'inch and a HYDRAULICS would claim a prior place, but as quarter in diameter; he filled the ball end part this arrangement would, of necessity, tend to of the tube with water, which had previously render the subject obscure and unconnected, it been deprived of air as much as possible; he will be advisable to connect these important then placed it under the receiver of an airsubjects and to treat them in th natural pump, and removed the pressure of the atmosorder; beginning with the weight and pressure phere: under this treatment, he observed that of water, and then showing the application of the water rose a little in the tube. On the conhydrostatic equilibrium in the construction of trary, when he placed the apparatus upon a conhydraulic machines.
densing engine, and by condensing the air in We had better in the first instance explain the receiver, increased the pressure upon the the nature of Auidity. A perfect freedom of water, he observed that the water descended in motion is essential to this state, and fluid bodies the tube. In this manner he proved that water are usually divided into elastic, and non-elastic. expanded one part in 21,740, when the pressure Air is an example of the first, as its bulk may of the atmosphere was removed; and submitted be lessened by augmenting the pressure, and en to a compression of one part in 10,870, under larged by diminishing the compressive force. the weight of a double atmosphere. He also Water, on the contrary, is said to be non-elastic, observed, that water possessed the remarkable or incompressible, not because it is absolutely property of being more compressible in winter so, but beoause its compressibility is so very than in summer; contrary to the effect on spirit small, as to make no sensible difference in our of wine and oil of olives. Lest it might be calculations, relative to its weight or motion. supposed the compressibility, thus discovered,
The compressibility of water was a subject might be owing to air lodged within the fluids which engaged the attention of philosophers at employed, a quantity of water was caused to a very early period. The Florentine academi- imbibe more air than it contained in a precedcians, from the following experiment, inferred ing trial, but its' incompressibility was not that it could not be diminished in hulk: they increased. These experiments, although, upon took a globe of gold, which was the least porous the whole, so apparently decisive of the quesof any body at that time known; and, having tions they were instituted to determine, are not filled it with water, they closed it up. They yet to be received without some caution; and, then subjected the globe to a great compressive in particular, the remark that the addition of a force, which squeezed the water through its portion of so compressible a fluid as air did pores, before any indentation could be made in not render water more compressible than before, it. As a hollow sphere has a greater capacity is rather staggering; and is calculated to throw than any other form, under the same surface, a veil of doubt over all the rest. It remained, the academicians supposed that the compressive therefore, for future investigators to determine power, which was applied to the globe, must the data for this branch of the science; but, even either force the particles of the fluid closer toge- granting all the compressibility that has been ther, or drive them through the metal, before contended for, the quantity of it is too small to the globe yielded in the slightest degree to be noticed in practice. compression. With respect to its precise ob The piezometer employed by Mr. Perkins, in ject, therefore, this celebrated experiment is not his experiments on the compressibility of water, Vol. XI.