« ZurückWeiter »
ed neck of land. It is purely volca- circumference, and the names of a pic, and in every part of it are seen great many French and English tra huge columns of bafaltes, placed al- vellers were engraven on the bark. molt vertically, except towards the It is not true that the electrical malower part of the point of land, where chine cannot be excited in the torrid they are inclined at different angles. zone : ours produced abundance of The pentagonal form prevails, and the sparks. The thermometer, on the 15th stone itself is of a fine grain and dark of January, when we arrived, stood colour; it strikes fire with steel. at 16° above o. After that it rose
The mountain is covered in seve- to 23° and 24", when it again deral places with a reddish volcanic earth scended, and is now at 180 ; but in insoluble in acids, which I consider as the fun it gets up to yoo t. It is a true puzzolane earth, and have ac- true, that the fun paffes directly over cordingly employed it with great fuc- our heads, but luckily there reigns cess in repairing the royal cisterns; here almost continually a fine fresh the cement I composed of it has har- breeze, which moderates his heat. dened perfectly, and retains the water The air is very pure at Goree, exexceedingly well, though made with cept in the rainy season, which gener very bad lime.
ally begins on the 3d or 4th of July, We have visited the Magdalen Ines, and continues three or four months ; distant about a league and a half from in that time there falls about thirty. Goree : they are composed entirely of fix or forty inches of rain, which immense columns of basaltes, like those serves for the whole year. However, of the Vivarais, and of Auvergne: the I have feen it rain twice fince our arsea, by breaking with violence against rival, but every body was astonished these columns, has formed in some at it; and there are old men here places vait chasms, which have laid who pretend that their fathers had open the interior appearance of them feen snow fall; but this is hardly creto a great depth. It is very danger. dible, as the thermometer, for a long ous to come too near these vast and time, has not been lower than 120 deep precipices, where the fea breaks (54° F.). with dreadful noise. One of my com- Our negroes here produced fire by panions, as he was contemplating this whirling round a bit of stick in the Iublime spectacle, was reached by a nole of a piece of wood, and lighting wave which threw him down ; but at it a fort of tinder made of the down luckily, though much bruised, he got of a thistle. The sea abounds in fish up and made his escape before the are on these coasts, and I have feen three rival of the next wave.
hundred pounds of fresh fish fold for In these Magdalen Islands, I mea- a small knife with a black handle, such sured three Baobab trees *, each of as in France might be bought for two which was more than sixty feet in pence.
* Adansonia Baobab. Lin.
† The French make ́use of Reaumur's thermometer. The corresponding degrees in Fahrenheit are nearly as follow : 168 R. = 60% F. 24° R. = 70° F. 18° R. = 64°F. 40° R. = 104° F.
An Account of forme necu Experiments on the Production of Artificial Cold.
In a Letter from Thomas Beddoes, M. D. to Sir Joseph Banks, Bart.
R WALKER, apothecary to the stallization, produces cold during its
Radcliffe Infirmary here, has solution, he thought of adding this to been engaged upwards of a year in a his other powers, and July 18, 1786, feries of experiments on the means reduced the thermometer 46 degrees. of producing artificial cold, feveral of In this experiment the following prowhich seem to me to be very remark- portions were used : the temperature able, and such as, considering their of the air being 65°, to water four novelty, and the attention which has ounces, at 63°, were added, lately been paid to this subject, I flat. Of fal ammoniac 3 xi 2 ter myself will be found to deferie therm. sunk to 32°, S
that is, 31° a place among the Tranfactions of the Of nitre 3 x — to 24', that is, 80 Society over which you preside, OfGlaub. salts Z ij -10 17°, that is, 7°
Mr Walker, in his firft experiments, found, as Boerhaave had done before him, that fal ammoniac, as well as In this way he froze water on a nitre, well dried in a crucible, and re- day so hot that the thermometer in duced to a fine powder, will produce the shade stood at 70°. By first a greater degree of cold than if they cooling the falts and water in one bad not received this treatment. But mixture, and then making another of Boerhaave, by fal ammoniac, lowered the cooled materials, he sunk the the temperature of water only by thermometer 64 degrees, 28° ; whereas Mr Walker observed Aug, 28. The temperature of theair this thermometer to fall 32°, and being 65°, half an ounce of rectified when he used nitre 19o. It occur. fpirit of wine was diluted with three red to him, that the combination of ounces and an half of water, and imthese substances would produce a merfed in the same frigorific mixture. greater effect than either separately : When cooled to 24", it began to and he found that this was really the freeze. A quantity of the neutral case. A propofal for freezing water salts, likewise cooled in the mixture, in summer, mentioned by Dr Watson were put into the diluted fpirit, when (Essays, III. 139.) determined him the thermometer fell ro - 4%, so that to attempt the same thing in this way. the liquor was cooled 69 degrees. Accordingly, April 28, 1786, the Spirit of nitre, diluted in the manthermometer standing at 47o, he made ner described by Mr Cavendish (Phil. a solution of a powder, consisting of Trans. vol. lxxvi. part I.) having equal parts of sal ammoniac and nitre, reduced the thermometer to - 3o, in a baron, by means of which he fal ammoniac was added, upon which cooled some water, contained in a it fell to - 150 glass tumbler, to 220. To this he Nitrated volatile alkali, during its added some of the same powder, and solution in water, reduced the therimmerfed two very small phials in it ; mometer 35 degrees (from 500 to one containing boiled, the other un. 15°); but the cold was not increaboiled water ; when he soon found fed by fal ammoniac or nitre. the water in the phials to be frozen, the Mr Walker's most remarkable exur boiled freezing first.
periment was made on the 21st of Having observed that Glauber's March, 1787, when he found, that F 2
nitrous * Phil. Trans. vol. Lxxy11. Part U.
nitrous acid, when poured upon Glau- the largest pan. The third pan, conber's salt, produced effects nearly the taining the salts for the third mixture, fame as when it is poured on pounded was immersed in the liquor of the seice ; and that the cold, thus produ- cond pan; and the liquor for the third çed, is rendered still more intense mixture was put into wide-mouthed by the addition of fal ammoniac in phials, which were immersed in the powder.
second pan likewise, and floated round Mr Walker, by many trials, dif. the third pan. The fourth pao, which covered that the bcit proportion of was the smallest of all, containing its these ingredients is the following : cooling materials, was placed in the Of concentrated nitrous acid, 2 parts midit of the salts of the third pan. by weight, of water i part ; of this Of the materials for the mixtures mixture cooled to the temperature of to be made in these four pans, the first the atmosphere eighteen ounces, of and second consisted of diluted vitrioGlauber's falt a pound and ap half lic acid and Glauber's falt, the third (avoirdupois,) and of fal ammoniac and fourth of diluted nitrous acid, twelve ounces.
On adding the Glau. Glauber's salt and sal ammoniac, in ber's falt to the nitrous acid, thus the proportions afligned, diluted, the thermometer fell from The pans beir.g adjutted in the man+ 51° 10.- 1°, or 52 degrees; and ner above described, the materials of on adding the fal ammoniac it fell to the fist and largest pan were mixed :
9', that is full 60 degrees. Nic this mixture reduced the thermometer frated volatile alkali, employed instead to + 10, and cocled the liquor in the of fal ammoniac, produced a cold ra- second pan to' + 20; and the salts for ther more intense.
the second mixture, which were plaBy means of this mixture, in a ced underneath in the large veffel, very few minutes, in the elaboratory ncarly as much. The second mixture before the class, I froze some spirits was then niade with the materials thus above proof, diluted with an equal cooled, and it reduced the thermobulk of water ; and another gentle- meter to 3o. The ingredients of the man this day funk the thermometer third mixture, by immersion in this, 68 degrees.
were cooled 10 + 10°, and when mix, On April 20, 1787, Mr Walker ed reduced the thermometer to - 150, effc&ed the congelation of quicksilver The materials for the fourth mixture by a combination of these mixtures, were cooled by immersion in this third without a particle of snow or ice. mixture to about – 12°. On mixing When he began his experiment the they made the mercury in the ther. temperature of the mercury was 45°, mometer fink rapidly, and, as it apso that, the freezing point of that peared to Mr Walker, below – 40. metal being - 39', there were pro- Its thread seemed to be divided below duced 84 degrees of cold.
that point; but the froth occafioned This experiment was performed as by the ebullition of the materials pres follows : Four pans, of lizes progref- vented his making so accurate an obfively diminishing, so that one might servation as he could have wished. be placed within the other, were pro- The reason why this last mixture cured. The largest of these pans was reduced the thermometer more than placed in another vessel still larger, in the third, though both were of the which the materials for the second fame materials, and the last at a lower frigorific mixture were thinly spread, in temperature, Mr Walker imagines to order to be cooled. The second pan, have been partly, because the fourth containing the liquor (viz. vitriolic a- pan had not another immersed in it sid, properly diluted) was placed in to give it hcat, and partly becauso
the materials were reduced to a finer pearance of congelation took place powder.
with other proportions of acid and I should imagine, that mercury re- water, at other temperatures. duced to its freezing point will freeze Mineral alkali, when it retained its more quickly than water reduced to water of crystallization, added to some its freezing point ; because it appears, of these mixtures, heightened their from experiments on their capacity effects: But when it had lost this for boat, that the latter of these bodies water, it rather produced heat than bas so much more latent heat in its cold; and the fame thing is also true liquid state ; which greater quantity of Glauber's falt. This circumstance of lacent heat muit, as it becomes leads us, in some measure, to the sensible, more retard the congelation. theory of these phænomena. Water
I forbear to enumerate many vari- undoubtedly exists in a solid state in ations of these experiments which crystals ; it must therefore, as in oMr Walker has among his notes ; ther cases, absorb a determinate quanbut there is one mixture which, tho'tity of fire, before it can return to its its power is not equal to that which liquid state. On this depends the I have last described, may prove very difference between Glauber's salt and serviceable in experiments of this na- foslil alkali in their different states of ture, on account of its cheapness. It crystallization and efforescence. The consists of oil of vitriol diluted with fame circumstance 100 enables us to an equal weight of water : added to understand the great effect of GlauGlauber's falt, it produces about 46 ber's salt, which, as far as I recollect, degrees of cold. The addition of fal has the greatest quantity of water of ammoniac renders it more intense by crystallization. a few degrees. One remarkable cir- Those, therefore, who shall choose cumstance occurred to Mr Walker, to pursue the path which Mr Walker as he was endeavouring to ascertain has opened to them, would do well to the best strength of the vitriolic acid : try combinations of salts containing he happened to be trying a mixture of much water of crystallization ; but two parts of oil of vitriol and one of they must take care left the effect water, when he observed, that, at the should be diminished or destroyed by temperature of 35°, the mixture coa. the formation of compounds that fix gulared as if frozen, and the thermo- a smaller quantity of fire. It is, how, meter became stationary; but, on add- ever, but justice to Mr Walker to ob ing more Glauber's falt, it fell again, serve, that he has carried his experiafter some little time, but so great a ments in this way very far, and with cold was not produced as when this great ingenuity. circunstance did not occur, and when I have the honour to be, &c. the acid was weaker. The same ap
Obferuations on the Structure and Econonry of Whales. By John Hunter, Efq.
F. R. S.; communicated by Sir Jofeph Banks, Bart. P. R. S.
sea are much less known to us information fails; which must proba, than those found upon land ; and the bly ever continue to be the case, from economy of those with which we are our unfitness to pursue our researches beft acquainted is much less under in the unfathomable waters. ftood: we are, therefore, too often The anatomy of the larger marine
animals, when they are procured in a The animals of this order are in proper state, can be as well ascertain- fize the largest known, and probably, ed as that of any others ; dead struc- therefore, the fewest in number of all tare being readily investigated. But that live in water. Size, I believe, even such opportunities too seldom oc- in those animals who feed upon ocur, because those animals are only thers, is in an inverse proportion to to be found in distant feas, which no the number of the smaller ; but, I beone explores in pursuit of natural his- lieve, this tribe varies more in that tory; neither can they be brought to respect than any we know, viewing it us alive from thence, which prevents from the Whalebone Whale, which is our receiving their bodies in a state seventy or eighty feet long, to the Porfit for dissection. As they cannot live poise that is five or lix; however, if in air, we are unable to procure them they differ as much among themselves alive.
as the Salmon does from the Sprat, As the opportunities of ascertaining there is not the comparative difference the anatomical structure of large ma- in fize that would at first appear. The rine animals are generally accidental, Whalcbone Whale is, I believe, the I have availed myself, as much as pof- largest; the Spermaceti Whale the lible, of all that have occurred; and, next in size (the one which I examianxious to get more extensive infor- ned, although not full grown, was aa mation, engaged a surgeon, at a con- bout sixty feet long ;) the Grampus, fiderable expence, to make a voyage which is an extensive genus,
proto Greenland, in one of the ships em- bably from twenty to hfty feet long ; ployed in the whale fishery, and fur- under this denomination there is a nished himn with such necessaries as I number of species. thought might be requisite for exami. From my want of knowledge of the ning and preserving the more interest- different genera of this tribe of aniing parts, and with instructions formals, an incorrectness in the applicamaking general observations ; but the tion of the anatomical account to the only return I received for this expence proper genus may be the consequence; was a piece of whale's ikin, with some for when they are of a certain size, small animals sticking upon it. From they are brought to us as Porpoises ; the opportunities which I have had of when larger, they are called Grampus, examining different animals of this or- or Fin-fith. A tolerably correct anader, I have gained a tolerable accu- tomical description of each fpecies, rate idea of the anatomical structure with an accurate drawing of the exof fome genera, and such a knowledge ternal form, would lead us to a knowof the structure of particular parts of ledge of the different genera, and the some others, as to enable me io ascer- species in each ; and, in order to fortain the principles of their economy.
ward so useful a work, I propose, at Those which I have had opportu- some future period, to lay before the nities of examining were the follow. Society desoriptions and drawings of ing :
those which have come under my own , The Delphinus Phocæna, or Por- observation. poise. The Grampus. The Delphi- This order of animals has nothing nus Delphis, or Bottle-nose Whale. peculiar to fith, except living in the The Balæna Rostrata of Fabricius. fame element, and being endowed with The Balæna Mysticetus, or large the same power of progressive motion Whalebone Whale; the Physeter Ma- as those fish that are intended to move crocephalus, or Spermaceti Whale ; with a considerable velocity: for I be. and the Monodon Monoceros, or lieve, that all that come to the surface Narwhale.
of the water (which this order of