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EXPERIMENTS on the LOSS of WEIGHT in BODIES. (163) “ In a branch, which I cut from the electrical shock, even ad. through in such a manner as to though a very gentle one; but the leave it suspended only by a little state of the atmosphere was so un, of the bark no thicker than a favourable for experiments of this thread, the leaves next day did not kind, that I could not pursue them rise to high as the others; but they fo far as I wished, were green and fresli, and, on being " There are two other plants touched, moved, but in a much less mentioned as species of this genus degree than formerly.

by Linnels. The first, the Avera “ After fun-let the leaves go to rhoa Bilimbi, I have not had an fleep, first moving down so as to opportunity of seeing. The other, touch one another by their under or Averrhoa Acida, does not seem fides: they therefore perforin ra- to belong to the same class; nor ther more extensive motion at night do its leaves possess any of the of themselves than they can be moving properties of the Carammade to do in the day-time by ex- bola. Linnæus's generic descrip. ternal impressions. With a convex tion of the Averrhoa, as of many lens I have collected the rays of other plants in this country which the fun on a leaf, so as to burn a he had not an opportunity of seeing hole in it, without occafioning any fresh, is not altogether accurate. motion. But when the experiinent The petals are connected by the was tried on the petiolus, the ma- lower part of the lamina, and in tion is as quick as if frum Irong this way they fall off whilf the percussion, although the rays were ungues are quite distinct. The stapot fo much concentrated as to mina are in five pairs, placed in cause pain when applied in the the angles of the gerien. Of cach fame degree on the back of the pair only one stamen is fertile, or hand; nor had the texture of the furnished with an anthera. The petiolus been any ways changed filaments are curved, adapted to the by this ; for next day it could not Mape of the germen. They may be distinguished, either by its ap- be preffed down gently, so as to pearance or moving power, from remain ; and then, when moved a chofe on which no experiment had little upwards, rise with a spring, been made.

The fertile are twice the length of 56 The leaves move very fast those destitute of antheræ."

Ao ACCOUNT of some EXPERIMENTS on the LOSS of WEIGHT

in BODIES, on being melted or heated. By GEORGE FORDYCE, M. D. FR.S.

[From the same Publication. ]

16 A Lthough I have made many contradiction in them. I shall con.

A experiments on the subject tent myself with relating the folof the loss of weight in bodies on lowing one, which appears to me being melted or heated, I do not conclufixe in determining the loss think it worth while to lay them all of wciglir in ice when thawed into before the Society, as there has water, and subject to the least fale Aot appeared any circumstance of lacy of any I bave hitherto made,

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in shewing the loss of weight In ice for about a minute, I found it be. on being heated.

gan to lose weight, on which I « The beam I made use of was immediately took it out, and placed so adjusted as that, with a weight it at a distance from the beam. I between four and five ounces in also immediately plunged a there each scale, zoo part of a grain mometer in the freezing mixture, made a difference of one division and found the temperature 1o de. on the index. It was placed in a grecs; and on putting the ball of rooin, the heat of which was 37 the thermometer in the hollow at degrees of Fahrenheit's thermo- the bottoin of the glass veflei, it meter, between one and two in the newed 1 2 degrees. I left the whole afternoon, and left till the whole for half an hour, and found the apparatus and the brass weights ac. therinometer, applied to the hol. quired the same temperature. low of the glass, at 32°. Every

" A glass globe, of three inches thing now being at the same temdiameter nearly, with an indenta- perature, I weighed the glass contion at the bottom, and a tube at taining the ice, after wiping it carethe top, weighing about 451 grains, fully, and found it had lost and had about 1700 grains of New. five divisions ; so that it weighed river water poured into it, and was ir, all but one division, more than hermetically sealed, so that the when the water was fluid. whole, when perfectly clean, weigh. " I now melted the ice, except. ed 2150 of a grain exactly ; ing a very sınall quantity, and leit the heat being brought to 32 de- the glass veffel exposed to the air grees, by placing it in a cooling in the temperature of 32 degrees mixture of salt and ice till it just for a quarter of an hour: the little began to freeze, and shaking the bit of ice continued nearly the whole together.

fame. I now weighed it, after “ After it was weighed it was carefully wiping the glass, and again put into the freezing mix- found it heavier than the water was ture, and let stand for about 20 at first, one divilion of the beam. minutes ; it was then taken out of Lastly, I took out the weights, the mixture : part of the water was and found the beam exactly ban found to be frozen ; and it was lanced as before the experiment. carefully wiped, first with a dry • The acquisition of weight linen cloth, and afterwards with found on water's being converted dry washed leather; and on putting into ice, may arise from an increase it into the scale it was found to have of the attraction of gravitation of gained about the să part of a grain. the matter of the water; or from This was repeated five times : at some substance imbibed through cach time more of the water was the glass, which is necessary to frozen, and more weight gained. render the water solid. In the mean time the heat of the " Which of these positions is room and apparatus had sunk to true may be determined by formthe freezing point.

ing a pendulum of water, and an« When the whole was frozen, other of ice, of the same length, it was carefully wiped and weighed, and in every other respect fimilar, and found to have gained 17 of a and making them fwing equal arcs. grain and four divitions of the in. If they mark equal times, then dex. Upon standing in the scale certainly there is lome matter added

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165) to the water. If the pendulum of cause of the gain of weight in the ice is quicker in its vibrations, conversion of water into ice in a than the attraction of gravitation is glais veffel hermetically sealed. increased. For there is no pofition “ I. Thall only observe, that heat more certain, than that a single certainly diminishes the attractions particle of inanimate matter is per- of cohesion, chemistry, magnetism, fectly incapable of putting itself in and eleciricity; and if it should motion, or bringing itself to rest; also turn out, that it diminishes the and therefore that a certain force attraction of gravitation, I mould applied to any mats of matter, fo not helitate to consider heat as the as to give it a certain velocity, will quality of diminution of attraction, give half the quantity of matter which would in that case account double the velocity, and twice the for all its effects. . quantity, half the velocity ; and We come, in the next place, generally a velocity exactly in the to take notice of the second part of inverse proportion to the quantity the experiment, viz, that the ice of matter. Now, if there be the gained an eighth part of a grain on fame quantity of matter in water being cooled to 12 degrees of Fah. as there is in ice, and if the force renheit's thermometer. In this of gravity in water be rico part case, a variation may arise from the less than in ice, and the pendulum contraction of the glass vessel, and of ice swing feconds, the pendulum consequent increase of specific gra. of water will lose goo of a se- vity in proportion to the air. But cond in each vibration, or one fe- it is unnecessary to observe, that cond in 28000, which is almost this would be só very small a quan. three seconds a day, a quantity tity as not to be observable upon a ealily measured.

beam adjusted only to the degree of “' I shall just take notice of an fenfibility with which this experi. opinion which has been adopted by ment was tried. In the second fome, that there is matter absolute- place, the air cooled by the ice ly light, or which repels instead of above the scale becoming heavier attracting other matter. I confess than the surrounding atmosphere, this appears abfurd to me; but the would press upon the scale downfollowing experiment would prove ward with the whole force of the or disprove it. Suppofing, for in- difference. If a little more than stance, that heat was a body, and half a pint of air was cooled over absolutely light, and that ice gain the scale to the heat of the ice and ed weight by losing heat ; then a glass containing it, that is, 20 de. pendulum of ice would swing grees below the freezing point, the through the same are in asso less difference, according to general time than a similar pendulum of Roy's table, would have been the water ; for the same power would eighth part of a grain, which was not only act upon a less quantity of the weight acquired; but the air matter, but a counter-acting force within half an inch of the glass would also be taken away.

vessel being only one degree below • Till the experiment of the the freezing point, I cannot conpendulum can be made, or some ceive, that even an eighth part of a other equally certain be suggested pint of air could be cooled over the and made, it would be wasting time Icale to 20. degrees below the freez. to enter into conjecture about the ing point; nor thas the whole dif.

ference

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Hate of decomposition, in which the may be partly, but not so perfeilly most refrangible rays escape in the decomposed as itself; for the rios greatest abundance; but of these lence of the heat will be found to rays the green escape most plenti. lesien in its effects the nearer it apfully through the unignited vapour proaches to the centre of the suband that portion of the atmosphere Itance which is exposed to it. which separates the eye from the Hence we are to consider the parts faine. The peculiarity which I which are juít corered by the ese have now endeavoured to account ternal surface as having lost less of for may be observed in the greatest their co.nponent light than the ea. perfection in brass founderies. The ternal surface itself. Or the former heat in this instance, though very may retain the green ravs when the Strong, is scarcely adequate to the latter has loft both indigo, violet, decomposition of the inetallic va- blue, and green. pour which escapes from the melt. " 3. Those parts which are ed brass. A very singular flame nearer the center of the body thaa therefore appears to the eye; for either of the preceding must, 25 while its edges are green, its body thov are farther from the greatest is such as to give the objects around violence of the heat, have lost piisa a very pallid or ghaftly appearance, portionably fewer of their rits, which is the consequence of its Or while the more external parts wanting that portion of red rays may have lost all but the red, theio which is necessary to make a perfect may have toit only the indigo and white.

• violet. " The most fingular phænome. " 4. The most central pirts non attending a burning body is may he unaffected by the hea; perhaps the red appearance it af. and whenever the fire does reach fumes in its last stage of combustion. these parts, they will immediately The preceding facts and observa- discharge their indigo rav's, and be tions may, I think, help us to ex: decompo'ed in the gradual manner plain it,

which I have already deicribute " ]. After a body has continuça A piece of rotten wood, u hilit bure. to burn for some time, its external ing, will cxemplify and confirm the surface is to be regarded as having preceding illustration. When in. Jost a great portion, if not the Huenced by the external air only, whole of those rays which the first if examined through a prism, no application of heat was able to ses rays will be found to escape but the parate. But these rays were the orange and the red. By blowing indigo, the violet, the blue, and upon the burning wood with a pair perhaps the green. Nothing, there: of bellows, the combustion, being fore, will remain to be separated, increased, will affect those internal but the yellow, the orange, and parts of the body which were not the red. Consequently the com- acted upon before. These parts, busțion of the body, in its last state therefore, will begin to lose their of decomposition, can assume no light, and a prism will shew the other than a reddish appearance, green, the blue, the violet, and in: But,

digo, all appearing in succeßion. 62, Let us consider the exter: Appearances limilar to the precede nal surface of the combustible as ing may be observed in a common annexed to an inner surface, which kitchen fire, When it is fainter,

thing shews more clearly the Now- to the furface, af a temperature infeness with which heat is imparted to rior to that of the surrounding air. a denser substance, from one that is By this means the small quantity highly rarefied, than a circumitance of heat which penetrated the ikin mentioned in the paper in question : would be immediately carried off, " that even the imall quantity of and transferred throughout the bomercury, contained in a thermome. dy: and it would have required the ter which the gentlemen carried space of many hours, before the with them into the room, did not whole mass could have received any arrive at the degree to which the considerable increase of heat. air was heated, during the whole “ It has been adduced, in proof time they remained there."

of the existence of the power of the II. Another cause which, in living body to generate cold, that the given situation, would diminish frogs, lizards, and other animals of the effect of the heated air, is, The the same fort, poffefs it; for if evaporation made from the surface of touched, they feel cold. This the body.

proves only, that their heat is less "That evaporation produces a than that of the hand, with which considerable abforption of heat, is they are felt; and perhaps less than well known : and, in making the that of the air, when the trial is experiments, there is reason to be made. lieve, that it took place in a confi- " But it is extremely probable, derable degree. Dr. Fordyce, anxie that no animal whatever can live in ous perhaps to establish his general health, for any considerable time, law, seeins unwilling to allow its in an atmosphere of a temperature influence. But when it is considere superior in heat to that of its own ed, that by the operation of the blood. Thus we find, that the ani. heat, the force of the circulation mals in qucstion hide themselves in was increased, the pores of the skin the day-time among thick grass, relaxed, and the pressure of the in- where there is a great evaporation ; ternal air diminished; when we are and in places into which the rays of told, that a turgescence of the veins, the sun cannot penetrate. Worms, and an universal redness of the sur. in hot weather, during the day, lie face of the body, took place; we deep in the ground; but in the are compelled to refuse credit to the night-time, when it is cool, rise to aflertion, even of Dr. Fordyce, that the surface to refresh themselves in there was no evaporation. The eva. the dew. When frogs, worms, and poration must have been great, and such other animals, are exposed to would diminish the effect of the ex- air warmer than their blood, its internal heaç by surrounding the sur. fluence is counteracted by the same face with a cool atmosphere, from causes which counteract its influ. its temperature fit for the absorption ence on the human body, the evaof heat, and from its rarity, unfit poration from the surface of their for the ready transmission of it into bodies, and the coldness of their the body.

blood. Such accidental exposure " III. But another very power- happens more frequently to them, ful cause of the body's having pre- than to the human species ; and, served its temperature in the given from the inferiority of their fize, tituation, remains to be goticed; they would be sooner heated which is, The fuccefive afflux of blood through, and leis able to relist the

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