and who has not endeavoured to efcape but this is difficult. It still remains to give an account of the Jews, who were formerly exceedingly numerous in this empire. When they were profcribed in Spain and in Portugal, a vaft number of them came hither, who flocked into the towns and fpread themselves over the country. It is to be prefumed, both from their own account, and the extent of the quarters that were allotted to them, that their numbers must have exceeded thirty thousand families; of thefe, there does not now remain a twelfth part; the reft have either changed their religion, or funk under oppreffion, or fled from the exorbitance of the taxes and impofts to which they are fubjected. The Jews poffefs neither lands nor gardens; they cannot enjoy fecurely the fruits of their industry; they are allowed to wear black cloaths only; and they are not permitted to pafs the mofques, or through the freets where there are fanctuaries, except with naked feet. The lowest of the Moors think they have a right to maltreat a Jew, who dares not defend himself, for the law and the judge are always in favour of the Moors. Notwithstanding this state of oppreffion, the Jews contrive to live here tolerably; as they have a genius for commerce and merchandize, they manage with great addrefs their traffic with the Moors, and profit by their ignorance. Many of them purchase the productions of the country, which they fell again. Some are courtiers; fome have intercourfe and carry on trade with Europe; fome are goldfmiths, armourers, tailors, carpenters, and mafons. As they are more induftrious and more ingenious than the Moors, they are employed by the Emperor in levying his cuftoms, in the coining of money, in all affairs relating to his commercial contracts with Europeans, as well as in all his negociations with the European courts. It is evident that, in this fort of tem porary administration, and in the intrigues which it renders neceffary, they have opportunities of doing fome good, and much ill; and they manage matters with fuch dexterity as to be gainers either way: fo that if the Jews are harraffed, they find, in the refour. ces of their induftry, the means of indemnifying themselves for the mortifications they endure. The Jewish women are in general handsome and fair; they have very fine eyes; they have a paffion for drefs; and are the more difpofed to gallantry, that, among the common people, the hufbands are fomewhat more than indulgent. There are, however, many families of this nation that live with great circumfpection. As the Jews, in the empire of Morocco, inhabit diftinét quarters, they obferve the ceremonies of their reli gion with fufficient freedom. It would even feem that they have multiplied their fuperftitious practices by the communication they have had with ftrangers fince the deftruction of their own empire. Their rabbis, who oppofe to every diforder nothing but their prayers, encourage thefe errors without endeavouring to root them out. As they enjoy the ecclefiaftical immunities granted them by their law, these doctors are exempted from the national impofts paid by the community: this exemption, which multiplies the number of rabbis, makes the burden of the impofts upon the labouring people more infupportable; while the rabbis, enriched as it were by the public poverty, engage in trade with uncommon advantages. Here the Jews speak the Arabic language, and all of them understand the Hebrew, from the analogy there is between the two languages: every where elfe Hebrew is their learned language, which none but the rabbis understand. Amidst all their perfecutions the Jews have preferved their religion, and in all their wanderings they have carried carried along with them their cuftoms. In Morocco they are more fcrupulous than in other places in obferving thofe which were anciently practifed at the death of relations: the fatal moment is announced by loud cries and lamentations; mourners for hire are engaged, who come and fing in a fort of measure which is marked by beat ing with the hand, and this feems to denote the degree of their grief; the relations of the deceased tear their hair and beat their breasts, and join in the chorus of this lugubrious concert, which is repeated on the day of the interment. Six days of mourning are afterwards religiously observed, during which they go with naked feet, and dare neither fhave themselves nor change their cloaths. On the feventh day, the cries and the mufic begin again, well as on the firft of the eleventh month, which is the last of the mourning. At thefe funeral ceremonies, the mourners chant stanzas containing moral fentences with regard to life and death, and when they are in the humour, they fing extempore verfes in honour of the deceased. The Effects of Heat and Cold on the Refpiration of Fishes. By M. Brouffonet *. ISHES cannot fupport, in water, a degree of heat equal to that which quadrupeds can endure in the air: the difference, indeed, in this refpect, is very confiderable: for the latter feem not at all affected in an atmosphere, the heat of which, if communicated to water, would be fufficient to kill any fishes confined in it. Man, too, is able to bear, without inconvenience, a very great degree of heat. Some English philofophers, while they were able to ftand in an atmof phere heated to the 211th degree of Fahrenheit's thermometer, could not hold their hands in water heated only to 125°; a temperature which would undoubtedly have been fufficient to deftroy the organization of fishes. We have accounts, however, of fome of these animals having been found living in pretty warm water. The ancients remarked this fingularity. Ælian speaks of a lake in Lybia, the water of which is very warm, and the fishes it contains die if they are tranfported to a colder place. We find fimilar obfervations in the writings of St Auguftin and Cardan. Shaw, in his Travels to Barbary, mentions fome warm fprings, in which he had found feveral fishes of the perch kind. Lately, M. des Fontaines, of the Academy of Sciences, has observed the fame thing in the neighbourhood of Cafza. Reaumur's thermometer rose in a spring there to 30°; (86 of Fahrenheit) and I imagine that Elian's obfervation was made on the fame fprings. We have accounts of living carp found in the mineral waters of Lucas, the heat of which is equal to that of the human blood. Valifnieri too fays, that he has feen living fishes in hot mineral waters, and Conringius mentions the fame phenomenon. Anderfon relates a fimilar fact obferved by. him in Iceland. It is needlefs to quote a great number of other authorities that might be brought, because hardly any of the authors have determined with accuracy the degree of heat in the waters they mention. But among all the observations related with regard to this phenomenon, that of M. Sonnerat is certainly the most furprifing. He fays, that he found at Manilla, fifhes living in water that raifed Reaumur's thermometer to 69o, (154° of Journal de Phyfique. (154° of Fahrenheit.) My own experiments have not fhewn me any thing like this. Mufchenbroeck has faid, that fishes perish when Fahrenheit's thermometer ftands at 111°; he has feen a very lively perch die in three minutes in water of the ten rature of 96o; and he adds, that these animals lived very well in water of 72°. It is very difficult to determine pofitively the different degrees of heat that each species is able to bear; they differ according to the feafon, and according to the form of the organs of refpiration. On the 20th of June 1784 I put two epinoches (ftickle-backs) in a large vessel full of water, the temperature of which was 58°*. I increafed the heat gradually, till it arofe, in two hours and a half, to 82°; the animals then appeared exceedingly agitated, and were just about to expire, when I took them out, put them into fresh water, and they revived in a few mi Outes. The 10th of November 1784, into a yeffel that had a hole in it to permit the gradual leaking of the water, I put a carp, fome bleaks, gudgeons, and a few fishes of the perch kind. The water was taken from the Seine; the thermometer in it stood at 41°, and the bottom was covered with fand. At five and twenty minutes past noon the thermometer was at 44°, at half an hour 46°, &c. My experiments lafted till forty-five minutes paft four o'clock, and 1 carefully marked the degree of heat every five minutes, pouring in a little fresh water from time to time. When it reached 58°, the little fishes began to rife to the furface of the water; they were agitated and gave figns of much uncafinefs, though the water of the Seine is much warmer in Summer. At 69°, the bleaks loft their equilibrium, and were almoft dead; at 719, the perches turned up their belly, and remained motionlefs; the gudgeons, which were a little larger, did not appear to fuffer much till the heat arofe to 73°; but, the carp ftill appeared unaffected, except as to his refpiration, which be came more frequent. I kept the wa ter for fifteen minutes at 82°, when the carp began to fhew fymptoms of uneafinefs, and loft his equilibrium ; and at laff feemed dead, or at least in afphexia. I took him out and pur him into fresh water, where it was a long time before he recovered. I in creafed the heat of the water gradual ly, fo that it was four hours and a half before it reached 82 degrees. I am perfuaded that, with certain precautions, fishes might be brought to live in water ftill warmer than this. I intend to profecute thefe experiments, and to vary them in different ways. If we fuppofe that fishes, (which is to be prefumed from the refult of the experiments I have juft detailed) cannot live in water heated beyond 86° ; and if we alfo confider that they can▲ not exist in water when its tempera ture is fome degrees below the free zing point, it would follow, that the extremes of heat and cold, which these animals can fuftain, are confined with in a very narrow range, perhaps 56° at the utmost; a range which, when compared with that in which warmblooded animals can live and profper,* is indeed very inconfiderable: but it will be found always to bear a propor tion to the vital heat, which in fishes is even inferior to that of reptiles and oviparous animals. Martin found that the heat of the blood in many falt-wa, ter fishes was not more than one degree beyond that of the element in which they lived. The fame experiment, repeated on the trout, and other fresh-water fishes, furnished him with The following experiments were made with Reaumur's thermometer; but as that inftrument is little in ufe in this country, it was thought better to infert the correfponding degrees in Fahrenheit, even though there fhould be fomelittle inaccuracy in the comparifon, which, it is hoped, the reader will make allowance for. ED. with the fame refult. Mr John Hun- the heat of the element they live in by one degree only, or one degree and a half, while the cetaceous animals which refpire air have their blood as warm as that of man. ter has feen Fahrenheit's thermometer, introduced into the ftomach of a carp, rife from 654o, the temperature of the water, to 69°, that is, 34°. But it is to be obferved, that this fish was then out of the water; a very effential circumstance, which would have a great effect on the refult of the experiment. I plunged a thermometer into the body of feveral fmall fifhes taken from the Seine, and held them in water during the experiment; the heat never exceeded that of the water 1, and in those that were weakly, never more than one degree. A pretty large, but weak eel, raised the thermometer only 1 carps half a degree, and fometimes 3°. In general, the heat of fishes is inconfiderable, and, I believe, we may reasonably doubt the obfervation of Olafsen, who maintains, that he has remarked a very fenfible degree of heat in the blood of a fpecies of fhark (fqualus glaucus). Fishes fuffer a great waste of animal heat, as the water is continually robbing them of a large quantity, and the portion of that fluid which is immediately in contact with them is accordingly warmer than it is at a diftance. It has been obferved, that a carp, plunged into a frigorific mixture, preferved all around it a quantity of water in a fluid ftate, though the rest of the liquor was entirely frozen. I plunged a thermometer into the body of a porpufs at a wound it had juft received in the fide of the neck, and which poured forth a deal of blood: the animal was already dead, and yet the thermometer rofe to 83°, and remained at this height when immerfed in the genitalia. The temperature of the atmosphere was that day 56°, and that of the water of the fea near the fhore 55°. Fishes do not experience in water fuch viciffitudes of heat and cold as quadrupeds do in air. The tempera ture of water at a certain depth, seems to be almost always the fame: this the Count de Marfigli afcertained by experiment in fea-water, and M. de Sauffure has lately confirmed it. That of rivers, when the furface is frozen, is, in the middle, fomewhat above the freezing degree. In great heats the temperature of water is always below that of the air: and accordingly it would feem that its animals are more apt to be injured by excess of heat than of cold. Fishes are, however, affected by the variations of the atmosphere, and when it is inclined to rain they come up to the furface. This fact did not escape Bacon, and he cites it as a proof of the great influence the air has on animals that live in water. But would it not be a more fimple account of the phenomenon to attribute it to the wea ther, which, at that time, determines the infects to fly low, fo that they come within the reach of fishes at the furface of the water? and this is the more probable, as these make the chief food of river fishes. We cannot attribute the evolution of heat in fifhes to any other caufe than refpiration. The phenomena by which Meff. Lavoisier and de la Place have explained the production of heat in animals that live in air, are obferved alfo in fifhes, though less fenfibly: the differences in the heat of animals that breathe air and those that breathe water are particularly remarkable when we compare the true fifhcs with the cetaceous animals, which all natural- To the great variations of the atifts, before M. Briffon, arranged in the mofphere is to be afcribed the migra fame clafs. Both inhabit the fame e- tion of thofe prodigious fhoals of her lement, yet thofe that are furnished rings which the cold annually forces with gills and refpire water, exceed to go in queft of more temperate feas Vol. VII. No 38. than than thofe of the Pole: but we have as yet hardly any obfervations on these periodical migrations. Fishes destined to remain always in the neighbourhood of the fhores likewife feel the rigour of the atmosphere, and fhelter themfelves in the mud, where the greatest part of them remain in a state of torpidity, like that which in Winter happens to the bear, the dormoufe, the marmot, &c. The ancients have taken notice of this periodical fleep; the moderns have made no obfervations on it that deferve any particular attention. It is eafy to know the fifhes of this order, by the elongated form of their body, by the absence of the ventral fins, and by the undulatory motions which they are obliged to perform in order to sustain themselves in the water. stances there are many that become noxious to fishes. Their deleterious property acts for the most part on the organs of refpiration in thefe animals which more rarely happens to fuch as live in air. Nature has, however, endowed fishes with a power fufficiently great to refift fome of the changes that may happen to water: they pafs, for inftance, freely from falt water to fresh, and from fresh to falt. We know the prodigious quantities of falmon, fhads, and lampreys, that every year abandon the fea and afcend the rivers; and carps, on the contrary, leave the fresh waters and gain the waters of the fea. If we attend to the difference which the alternate refpiration of fresh and of falt water must produce in these animals, we will have an idea of the power with which we have faid they I do not confider as torpidity, pro- are endowed of refifting the changes perly fo called, that state which many water is liable to; a power in this cir authors affirm they have obferved in cumftance far beyond that obfervable fishes entirely frozen and then resto in other animals which could not fup red to life. Perhaps the opinion is port fo violent and so sudden a change founded on what fometimes happens to in the air. This may account for the the parts of animals with warm blood,, lefs perfect organization of the parts which recover life after having been deftined for the refpiration of fishes ; frozen but it must be observed, that as this ftructure defends them from the blood of these last is very much the too great influence which the va warmer, and that it is impelled with rious and vitiated states of that ele much greater force through the veffels ment would otherwise have on their than in fishes. But, however this may organs. be, Mr John Hunter, who attempted the fame experiment, never could fucceed; for when he had frozen the tail of a fish, the animal never recovered the use of that part. Water affects, in a much greater variety of ways, the organs of refpiration in fifhes, than the air does thofe of the hot-blooded animals. Many individuals, after having breathed for a long time in a certain quantity of water, fo corrupt it as to render it unfit for further refpiration, in the fame manner as hot-blooded animals vitiate the air when they are crowded into one place. Water holds in folution a much greater number of fubftances than air does, and amongst thefe fub When I put fishes into diftilled water they lived; they did at first indeed fhew manifest signs of uneasiness, but after having continued in it for fome time, it did not feem to affect them much. Their motions had perhaps difpofed the water to imbibe that proportion of air which is neceffary for their refpiration. A little fifh, however, inclosed in a corked bottle, containing a quart of distilled water, lived in it for thirty hours. Syrup of violets, poured in fmall quantity into dif tilled water which contained living fishes, did not in the leaft change its colour; it indeed grew a little green fome time afterwards, which may be afcribed to the alkalefcent part of the mucus |
