Abbildungen der Seite
PDF
EPUB

1

power.

from hard earth, and ftony substances. constantly the same in every part of the That fingular fofil, called Asbestos, globe. Spars, crystals, and precious molt evidently grows from an earthy stones, are invariably the same for ever. root. Those productions, named Brain- Skins,fells, feathers,&c are always the Stones, have all their radical parts by same for the same animals. All matter, which they grow from submarine rocks. while it retains it's original form, will Pyrites, or fire-stones, exhibit the root conftitute the same kind of body. If from which they shoot upwards in the form of a scollop-shell be impressed curious forms and configurations; and upon the substance of hard stone, it even many common pebbles have the will make a scollop-stone, though not most evident signs of a root or radical a scollop-shell: and many such forms part from whence the substance of the of shells we find every where existing Itone gradually proceeded. Metals, too, in mere earth, fand, loam, pebbles, in their purest forms, actually present the hardeit rocks, and on the highest us with arborescent vegetations: thus mountains. But the perfect imprefwe find real sprigs and branchery of fion of a cockle-shell in the middle of maffy and malleable copper in the a small pebble, scarce half an inch mines. All kinds of metals grow in wide, and of the very fame matter with their

proper earths or ores; and silver, the pebble, is an infallible proof that in particular, discovers as perfect a ve- it was solely the effect of this plastic getation, in branches and leaves, as

That this power forms shells even fern: gold grows in grains of dif- at land the same as those in the sea ferent sizes; tin is frequently found when it has the fame materials to work in the form of pebbles; and iron in upon, is evident from numberless small that of very large stones of the pebble shells conftantly formed from the spray kind. The copperas-stone evidently of the sea, at the distance of a mile from grows from a root; as well as that that element; and though they are decalled the Starry Waxen Vein, which stroyed every year by the ploughing of exhibits, when broke, a most curiousir- the ground, they are yet as constantly radiation in the form of a star. Num- regenerated. In many parts of the berless other instances might be ad- earth, fnells are formed in beds withduced, to prove the existence of this out the least admixture of earth be universal power of vegetation, in and tween them

Some hard ftones conthrough all parts of the earth, and the fift of nothing but shells throughout. various bodies it contains.

Lumps of soft moist fand, in a sandThe third great principle in nature, pit, appear with the lineaments of viz. an universal plastic power, is what, cockle-thells more or less visible; while in the beginning, gave birth to the by the touch only they would crumble beautiful order and frame of the mun- to powder. Not only the impressions dane fyftem, which we every where of shells, but of plants and animals of behold; and to that regularity, distri- many sorts, are found in all parts of bution, and distinction, observed to be the earth: the figures of the fern and permanent, and at all times uniformly the fish may as well be stamped in itone the fame, amongst all the myriads of as in the substance of a plant or anidifferent kinds and species of beings mal. We find nature, as it were, sporand bodies found therein. This power tive with this power, sometimes in preimpresses on matter those general marks senting us with the figures of many and characteristic forms, shapes, traits, forts of shells, animals, &c. which were and lineaments, by which bodies are never seen, or known to exist in any distinguished into their primary kinds part of the world. The most remarkaand classes, and which ever continue ble instance of this kind is the serpentthe same. Thus earth, fand, gravel, stone, coiled up in folds like a serpent clay, loam, &c. are in all parts of the or snake, from the smallest fize to the world of the same unchangeable form enormous one of two feet in diameter, and nature. Stones, flints, pebbles, both in soft sarth, and in the hardest flate, marble,marcasites, and metals, are stone,

PHILOSOPHICAL

ANIMALS

CUMSTANCES. BY ADAIRCRAW

IN

mode of it's operation, is so obfcure PHILOSOPHICAL TRANSACTIONS.

and incomprehensible. EXPERIMENTS ON THE POWER OF It appears to be accumulated in an

TO PRODUCE cold, immenfe quantity in the sun and WHEN PLACED IN CERTAIN CIR- fixed stars, from whence it's beneficial

influence seems to be continually difFORD, M:Di COMMUNICATED BY fused over the universe: it is the SIR JOSEPH BANKS, BÁRT. P.Rosu great instrument by means of wh

the changes of the seasons are effected; N the following paper I shall lay the diversity of climates is chiefly

before the Society the result of owing to the various proportions in Tome experiments, which I made in which it is distributed throughout the the course of the summer 1780, on the earth. If we add to this the mighty power that animals, when placed in alterations which have been procertain circumstances, possess, of pro- duced in human affairs by the introducing cold, having premised a few duction of artificial fire, by it's em. remarks on the progreflive improve- ployment in the separation of metals ments which have been made in the from their óres, and in the various knowledge of heat in general. arts which are subfervient to the coma

The opinions of the ancients, re- fort, the ornament, and the preserva specting the nature and properties of tion of the species, it will not ap. fire, confifted of bold conjectures, pear fürprizing that, in a rude and which seem rather to have been the ignorant age, this wonderful prinoffspring of a lively and vigorous ciple should have been considered as imagination, than of a juft and cor- endued with life and intelligence, and rect judgment: their ideas on this that it should have become the object subject being evidently derived, not of religious veneration. fo much from an accurate observa. In the dark ages the alchymists retion of facts, as from those fentiments garded pure fire as the residence of of admiration and awe which many the Deity: they conceived it to be of the phænomena of fire are calcu- uncreated and immense, and attrilated to excite. Thus, this element buted to it's influence most of the was supposed, on the original forma. phænomena of nature. Indeed, it tion of the universe, to have ascended is not wonderful that they should to the highest place, and to have oc- have assigned it a high rank in the cupied the region of the heavens; scale of being, as it was the great it was conceived to be the principle agent which they employed in the which first communicated life and chymical analyfis of bodies, and was activity to the animal kingdom; it the instrument of those discoveries was considered as constituting the ef- that attracted such universal admirasence of inferior intellectual beings; tion, and that enabled them so suća and, by many of the ancient nations, cessfully to impose upon the ignoit was reverenced as the Supreme rance and credulity of the times. Deity. Indeed, the profound vene- Upon the revival of literature, the ration with which the element of fire importance of this branch of science was contemplated, for a long succes- began very soon to engage the attenfion of ages, by a great part of man- tion of philofophers. It could not kind, appears to be one of the most escape the general obfervation, in a curious circumstances in the history penetrating and inquisitive age, when of ancient opinions... To account the powers of the human mind were for this, we may observe, that there employed with so much ardour and is no principle in nature, obvious to success in exploring the operations the senses, which produces such im- of nature, that the element of fire acts portant effects in the material system, a principal part in the system of the and which, at the same time, in the world; that by the influence of this ele. VOL. III.

meng

[ocr errors]

ment those motions are begun and exploded, since all were found to prosupported in the animal and vegetable duce fimilar effects upon the thermokingdoms, which are essential to the meter. The increase and diminution production and preservation of life; of temperature in the different seaand that it is the great agent in those fons and climates, the laws which successive combinations and decom- nature observes in the heating and positions, by which all things on the cooling of bodies, the melting, the surface of the earth, and probably vaporific, and shining points, and the throughout the universe, are kept in degrees of heat in the animal, the a continual fluctuation.

mineral and the vegetable kingdoms, But though the utility of this were accurately determined. In conbranch of science was perceived, yet sequence of the attention that was the progress that was made in the paid to this subject, many curious cultivation of it did not keep pace questions arose, which have long with the opinion which men enter- exercised the ingenuity of philofotained of it's importance. Our senses phers. That property of heat by inform us, that heat has a real exist- · which it is capable of expanding the ence, but they give us no direct in- denseft and hardest bodies; it's power formation with regard to it's nature in producing Auidity; it's tendency and properties: it is endowed with to an equilibrium; and the causes of such infinite subtlety, that it has been it's various distribution throughout called, by a very eminent philosopher, the different substances in nature, an occult quality; by some it has have become the objects of philosoeven been considered as an immaterial phical enquiry. It was observed, being. It is, therefore, with great that some bodies, on exposure to heat, difficulty, that it can be made the sub- become red and luminous, but are ject of philosophical investigation; and incapable of producing flame, or of hence the opinions of men concerning maintaining fire: that, on the con. it have been fluctuating and various, trary, others, by the application of and the words which express it vague fire, and the contact of fresh air, kin. and ambiguous.

dle into flame, and continue to emit The first Itep that was taken with light and heat, apparently from a a view to the cultivation of this branch fource within themselves, till they of science, was the construction of a are consumed. Hence arose the ques. machine for measuring the variations tions concerning the pabulum of of sensible heat; observing, that heat fire, the use of the air in inflammahas the power of expanding bodies, tion, and the distinction of bodies inand considering the degree of expan- to combustible and incombuftible. fion as proportional to the increase From the first dawnings of philo

heat, philosophers have endea- fophy it must have been perceived, voured by means of the former to that most animals have a higher temrender the latter obvious to the senses. perature than the medium in which

To this important invention, the they live; and that a constant succesauthor of which cannot be distinctly fion of fresh air is necessary to the traced, we are indebted for all the support of animal life. The causes of succeeding improvements in the phi- these phænomena have afforded matlosophy of heat. By means of it men ter for much speculation in ancient were enabled to establish a variety of as well as modern times: but the dif. interesting facts, and to bring some covery that animals have, in certain of the most obscure and intricate phæ- circumstances, the power of keeping nomena of nature to the teit of experi- themselves at a lower temperature

The opinion, that the heats than the surrounding medium, was inherent in various heterogeneous reserved for the industry of the presubstances differed from each other fent age. in kind, as well as in degree, was now This discovery seems originally to

ment.

have arisen from observations on the circulation of the blood, in conseheat of the human body in warm cli- quence of which the warmer fluids mates. It was mentioned by Gover- are continually propelled from the nor Ellis in 1758; it was taught by surface towards the centre, where Doctor Cullen before the year 1765; they are mixed with blood at a lower and at length it was compleatly efta- temperature; and hence the animal blished by the experiments of Doctor is slowly heated, in the same manner Fordyce in heated rooms, which were as the water in a deep lake, during laid before the Society in 1774. the winter, is slowly cooled, and not

In the course of these experiments, without a long continuance of frost the doctor remained in a moist air congealed, no part of it becoming heated to 130 degrees for the space of solid till the whole is brought down fifteen minutes, during which time the to the freezing point. thermometer under his tongue ftood at The following experiments were 100 degrees, his pulse made 139 beats made with a view to determine with in a minute, his respiration was but greater certainty the causes of the little affected, and streams of water ran refrigeration in the above instances. down over his whole body, proceed

To discover whether the cold proing from the condensation of vapour, duced by a living animal, placed in as evidently appeared from a similar air hotter than it's body, be not condensation on the side of a Floren- greater than what would be produced tine fal that had been filled with by an equal mass of inanimate matwater at 100 degrees.

ter, I took a living and a dead frog, He found, however, that he could equally moift, and of nearly the same bear a much greater degree of heat bulk, the former of which was at 67, when the air was dry. In this situa- the latter at 68 degrees, and laid tion, he frequently supported, naked, them upon flannel in air which had for a considerable time, without much been raised to 106 degrees. In the inconvenience, the heat of 260 de- course of twenty-five minutes the orgrees, his body preserving very nearly der of heating was as follows. it's proper temperature, being never

Air. Dead frog. Living frog. raised more than 2 degrees above the

Min. Deg. Deg. Deg. natural standard.

701 671 Various opinions have been enter

72 tained with regard to the causes of

3

72-1 691 the facts which were established by

4

73

70 these experiments. Some have at

95 tributed the cold solely to evapora.

814 781 tion, and have conceived that the The thermometer being introduced same degree of refrigeration would into the stomach, the internal heat of have been produced by an equal mass the animals was found to be the same of dead matter, containing an equal with that at the surface. quantity of moisture. Others have From hence it appears, that the affirmed, that the cold did not arise living frog acquired heat more slowly solely from this cause; but have main- than the dead one. It's vital

powers tained, that it depended partly upon must, therefore, have been active in the energy of the vital principle, the generation of cold. þeing greater than what would have To determine whether the cold been produced by an equal mass of produced in this instance depended inanimate matter.

solely upon the evaporation from the The ingenious Doctor Munro, of surface, increased by the energy of Edinburgh, ascribes the cold in the the vital principle, a living and

dead above-mentioned experiments to the frog were taken at 75 degrees, and

* In the two fallowing experiments the thermometers were placed in contact with the skin of the animals under the axilla.

were

In 1

2

102

68

[ocr errors]

25

[ocr errors]
[ocr errors]

Deg.

2

85

II

87

89

89 89

were immersed in water at 93 de- meter being closely applied to the grees*, the living frog being placed kin under the axilla, and so much of in such a fituation as not to inter- his head being uncovered as to al. Tupt respiration,

low him a free respiration. Dead frog. Living frog:

Min.

Deg.
Min. Deg. Deg.

In 5 the dog was 108 water 112
In 1 85

81

6

J09 U12 885

[ 08 112 the 3 907

respiration having become very rapid, 5 911

In thirteen minutes the dog was 6

108 degrees, water 112, the respira 8 91

tion being still more rapid, These experiments prove, that live In about half an hour the dog was ing frogs have the faculty of resisting 100 degrees, water 112; the animal heat, or producing cold, when in- was then in a very languid ftate. mersed in warm water; and the ex- Small quantities of blood being periments of Doctor Fordyce prove, drawn from the femoral artery, and that the human body has the same from a contiguous vein, the tempera power in a moist as well as in a dry ture did not seem to be much inair; it is therefore highly probable, creased above the natural standard, that this power does not depend solely and the sensible heat of the former upon evaporation.

appeared to be nearly the same with It may not be improper here to that of the latter. observe, that healthy frogs, in an at- In this experiment a remarkable mosphere above 70 degrees, keep change was produced in the appeare themselves at a lower temperature ance of the venous blood : for it is than the external air, but are warmer well known that, in the natural state, internally than at the surface of their the colour of the venous blood is a bodies; for when the air was 77 de- dark red, that of the arterial being grees, a frog was found to be 68, light and florid; but after the anithe thermometer being placed in con- mal, in the experiment in question, tact with the skin; but when the ther. had been immersed in warm water mometer was introduced into the sto for half an hour, the venous blood mach, it rose to 7016

assumed very nearly the hue of the It may likewise be proper to men

arterial, and resembled it so much in tion, that an animal of the same appearance, that it was difficult to species placed in water at 61, was distinguish between them. It is profound to be nearly 613 at the fur. per to observe, that the animal which face, and internally it was 664. was the subject of this experiment, These observations are meant to ex- had been previously weakened by tend only to frogs living in air or water losing a considerable quantity of at the common temperature of the at blood a few days before. When the mosphere in summer. They do not experiment was repeated with dogs hold with respect to those animals,' which had not suffered a similar evawhen plunged suddenly into a warm cuation, the change in the colour of medium, as in the preceding experi- the venous blood was more gradual; ments,

but in every instance in which the To determine whether other ani. trial was made, and it was repeated mals also have the power of producing fix times, the alteration was so recold, when surrounded with water markable, that the blood which was above the standard of their natural taken in the warm bath could readi; heat, a dog at 102 degrees was im- ly be distinguished from that which merfed in water at 114, the thermo- had been taken from the fame vein

In the above experiment, the water, by the cold frogo and by the agitation which it fufered during their immersion, was reduced nearly to gi degrees.

before

[ocr errors]
« ZurückWeiter »