any facts; neither will a rough estimate ferve the purpose of calculation. A beginning must be made by discovering the exact distance of the moon, and for this purpose it is neceffary firft to know the magnitude of our globe. Thus it is that Newton reafoned, but the measure he made ufe of depended on the false estimate of feamen, who allowed fixty English miles to a degree of the meridian, instead of near feventy, which is the truth. It must be confeffed that there was a more exact admeasurement extant. Norwood, an English mathematician, in 1636, meafured a degree of the meridian with fufficient precifion; but this work, though accomplished thirty years before, was unknown to Newton. The civil wars which had troubled the English nation, and which are always as pernicious to the fciences as to the ftate, had buried in oblivion the only measure of the earth which could be depended on, and the falfe eftimate of navigators continued ftill to be made ufe of. From this account the moon was found to be too near the earth, and the proportions enquired after by Newton did not turn out exact. He did not think himself at liberty to fupply any thing, or to accommodate nature to his own ideas; but, on the contrary, was ftudious to adjust his ideas to the ftandard of nature. He, therefore, abandoned this capital difcovery, which the analogy of the other heavenly bodies rendered fo highly probable, and which wanted fo little of being demonftrated. An inftance of candour which is very rare, and which alone is enough to add the great eit force to his opinions. But at length more exact measures were taken in France, and the demonftration of this theory was one of the confequences. A degree of the meridian was fettled at twenty-five French Leagues; the distance of the moon is about fixty femi-diameters of the earth, and from thefe data it was eafy to thew that the gravitating force of the moon towards the earth, when compared with that of a body at the earth's furface, is in the inverted ratio of the fquares of the distances from the center. LOND. MAG. Aug. 1783. By the order of time we approach near upon our own age, and, as the fcene expands before us, we become the lefs inclined to attempt any thing beyond a mere sketch. The prefent department of our work is not profeffedly hiftorical. Our chief endeavour will be to lay before our readers an account of the arduous undertakings, the difcoveries, and the researches which engage the attention of the vaft body of philofophers of the feveral academies and focieties of Europe. A familiar and rational account of every interesting philofophical event cannot but be ufeful as well as entertaining. In the mean time we fhall clofe this effay by taking a fhort view of the prefent ftate of philofophical knowledge. Natural Philofophy in its prefent ftate admits of two principal divifions, namely, into mechanical and chemical. Thefe divifions feem to be merely relative to the ftate of our knowledge. The mechanical part of Natural Philo. fophy is the doctrine of fuch motions as take place among maffes of fenfible magnitude. It therefore includes me chanics properly fo called, phyfical aftronomy, and hydroftatics. The che mical part is converfant with fuch motions as take place among maffes too fmall to come under the fenfes. We do not mention the metaphyfical part of Natural Philofophy, the bufinefs of which is to enquire into the origin of the properties of bodies, because it is almoft certain that the information neceffary for researches of this nature is placed beyond our reach. Now, the mechanical department is almost all dependant on very few first principles, and admits of demonstrations built upon thofe data. On thefe accounts it is in a state of very high improvement. But the chemical philofophy has not only the difadvantage of its agents being placed out of the reach of fenfe, but likewife labours under that of not having been in the hands of men of science till of late years. The cultivators of this fcience may be claffed from the relation their purfuits have to these feveral branches. Metaphyfics is at prefent very little attended to, and even very imperfectly P under understood in general. Men of real genius feem to think it too unprofitable a field to attempt its cultivation, and the books published on the fubject, if we except thofe of Locke, Hartley, and a very few others on the human understanding, are nothing more than an occafional reviving of the fuperficial opinions which the wanderings of the mind have produced in all cutivated ages, and which confequently may be found in the writings of the ancients. We may, therefore, divide philofophers into theorifts, empirics, and true philofophers. The age when the invention of theories, by which in this place we mean to imply hypothefes, met with the greatest encouragement was that in which philofophical liberty was in a great measure reftored to Europe by the deftruction of the empire of Ariftotle. But there have been and ever will be a confiderable number of men, who, fuppofing themfelves to poffefs genius, are willing to difplay it by a folution of thofe difficulties that more knowing or more modeft enquirers have left to the investigation of futurity. Thefe men imagine genius to confift in a certain infpiration or indefinable faculty that confers the power of excelling others without that labour to which common minds muft fubmit. But genius, in fact, can be nothing elfe but mental ftrength, and it is in vain for the poffeffor of ftrength to expect to go beyond others by any means befides that of exerting himself. An occafional work by writers of this clafs appears now and then among us; but as they generally difplay their ignorance of the first principles of that philofophy they attempt to confute, their works remain in oblivion, and are treated with too much contempt to receive even an anfwer by thofe who are capable of making the eafy conqueft. It will readily be imagined that this clafs of philofophers, if they may be fo named, are of no ufe to fcience.. The empirics are a fet of ingenious men, who receive vaft amufement by drawing fparks from an electrical ma chine, and he among them that can get the longeft fpark is reckoned the greatest philofopher. In proportion as their pretenfions to science are weak they attach the higher idea of excellence to things of fmall importance. The ufe of a new varnish, the bending of a wire, or the facility in using a hammer, file, pincers, or blow-pipe, are celebrated by thefe gentlemen in very pompous ftrains, there being a fort of mutual agreement among them to congratulate each other on their happy difcoveries. It is with reluctance that we are under the neceflity of including a confiderable number of chemifts in this clafs. We fhall, therefore, proceed to the true philofopher. The true philofopher is he who poffeffes abilities, industry, and literature. Since every thing in nature is performed by motion, it is abfolutely neceffary he should be deeply fkilled in mathematical fcience; and because in experiments the caufe is ufually very remote from the effect, his imagination fhould be lively, his habits of reafoning quick and accurate, and above all, his mind free from the influence of prejudice. Perfections which rarely center in one perfon, but when they do, they render him a bleifing to mankind, and an ornament to his age and nation. Such a man will be without arrogance, for he has kill to fee his own imperfections. He will be affable, mild, and patient in converfation, for he knows that the difcourfe of the moft ignorant may fometimes afford facts of the most interesting nature. He will be juft, benevolent, and fincere, for he is enamoured of truth. Even in the midft of the most fuccefsful refearch, when he begins to enjoy that fupreme delight which arifes from difcovery, he will never fuffer himself to be feduced by the delufions of fancy. All his productions will be chafte, ac curate, perfpicuous, and important. His reward awaits him; for he is entitled to confider himfelf as the bene factor of the world, and can fit down with the fatisfaction of faying, I have done my duty. NATURAL From the PHILOSOPHICAL TRANSACTIONS, Vol. LXXII. Part IIfor the Year 1782. ACCOUNT OF THE ORGAN OF HEARING IN FISH. As I do not intend to give, in this paper, a full account of this organ in any one fish, or of the varieties in different fish, but only of the organ in general, thofe, who may choofe to purfue this part only of the animal economy, may think it deficient in the defcriptive parts. If it was a difficult tafk to expofe this organ in fish, I fhould perhaps be led to be more full in my defcription of it, but there is nothing more eafy than the expofure of this organ in this animal in general. As this paper is to be confined to this order of animals, I may be allowed just to obferve here, that the clafs called fepia has this organ alfo, but fomewhat differently conftructed from what it is in the fifh." Ndered as TATURAL Hiftory has ever been confidered as worthy the attention of the curious philofopher, and therefore has in all ages kept pace with the other branches of knowledge; and as both arts and fciences have, of late years, been cultivated to a degree, perhaps, beyond what was ever known before, we find alfo, that Natural Hiftory has not been neglected; all Europe appears to be awake to it. In this inland it has been purfued with more philofophic ardour than what was ever known in any country. It has become the study of men of independent for tunes, who not only fpend their for tunes in the cultivation of this fcience, but have rifqued their health and lives in parfuit of it, fearching unknown regions to improve mankind, fettling. The organs of hearing in this latter correfpondences every where, fo as to order of animals are placed on the fides bring in its materials into this country, of the fkull, or that cavity which conin order to make it the school of Na- tains the brain; but the skull itself tural Hiftory. It is no wonder, then, makes no part of the organ, as it does that a spirit of inquiry is diffufed in the quadruped and the bird. In through almost all ranks of men; and fome fifh this organ is wholly furroundthat though many cannot purfue it ed by the parts compofing this cavity, themfelves, yet they are eager to know which in many is cartilaginous, the what is already known, choofing at fkeleton of these fish being like thofe leaft to benefit by the industry of others. of the ray kind; in others alfo, as in Thefe reflections have induced me cod, falmon, &c. whofe fkeleton is to trouble this learned Society with a bone, yet this part is cartilaginous. short account of the Organ of Hearing in Fish, it being still a fubject of great difpute, whether fish hear or not. Some time between the years 1750 and 1760, I obferved the organ of hearing in fifh; and from that time to this, I only confidered it as a link in the chain of the varieties in this fenfe in different animals, in which there is a regular progreffion, viz. from the moft perfect animals down to the moft imperfect poffeffed of this organ*. In fome fifh this organ is in part within the cavity of the skull, or that cavity which alfo contains the brain, as in the falmon, cod, &c. the cavity of the skull projecting laterally, and forming a cavity there, The organ of hearing in fish appears to grow in fize with the animal, for its fize is nearly in the fame proportion with the fize of the animal, which is not the cafe with the quadruped, &c. the organs being in them nearly as large P 2 in * Preparations to illustrate these facts have been ever since shewn, in my collection, to the curious both of this country and foreigners: when, in fhewing whatever was new, or supposed to be new, the ears of fish were always confidered by me as one important article, 108 in the growing fatus as in the adult. It is much more fimple in fifh than in all thofe orders of animals who may be reckoned fuperior, fuch as quadrupeds, birds, and amphibious animals, but there is a regular gradation from the first to fish. It varies in different orders of fish; but in all it confifts of three curved tubes, all of which unite with one another; this union forms in fome only a canal, as in the cod, falmon, ling, &c. and in others, a pretty large cavity as in the ray kind. In the jack there is an oblong bag, or blind procefs, which is an addition to thofe canals, and which communicates with them at their union. In the cod, &c. this union of the three tubes ftands upon an oval cavity, and in the jack there are two of thofe cavities; these additional cavities in thefe fish appear to answer the fame purpofe with the cavity in the ray or cartilaginous fish, which is the union of the three canals. The whole is composed of a kind of cartilaginous fubftance, very hard or firm in fome parts, and which in fome fifh is crufted over with a thin bony lamella, fo as not to allow them to collapfe; for as the skull does not form any part of those canals or cavities they must be compofed of fuch fubftance as is capable of keeping its form. Each tube deferibes more than a femi-circle. This refembles in fome refpect what we find in moft other animals, but differs in the parts being di ftinct from the skull*. Two of the femi-circular canals are fimilar to one another, may be called a pair, and are placed perpendicularly; the third is not fo long; in fome it is placed horizontally, uniting as it were the other two at their ends or terminations. In the fkait it is fomething different, being only united to one of the perpendiculars. The two perpendiculars unite at one part in one canal, by one arm of each uniting, while the other two arms or horns have no connection with each other, and the arms of the horizontal unite with the other two arms of the Near the union of thofe canals in- In the ray kind they all terminate in one cavity, as has been obferved; and in the cod they terminate in one canal, which in thefe fifh is placed upon the additional cavity or cavities. In this cavity or cavities there is a bone or bones. In fome there are two bones; as the jack has two cavities, we find in one of those cavities two bones, and in the other only one; in the ray there is only a chalky fubstance+. At this union of the two perpendiculars in fome fish enters the external communication, or what may be called the external meatus. This is the cafe with all the ray kind, the external orifice of which is fmall, and placed on the upper flat furface of the head; but it is not every genus or fpecies of fish that has the external opening. The nerves of the ear pass outwards from the brain, and appear to terminate at once on the external furface of the fwelling of the femi-circular tubes They do not appear above described. to pafs through thofe tubes fo as to get on the infide, as is fuppofed to be the cafe in quadrupeds; Ifhould, therefore, very much fufpect, that the lining of thofe tubes in the quadruped is not nerve, but akindof internal periofteum. As it is evident that fish poffefs the organ of hearing, it becomes unneceffary to make or relate any experiment made with live fish which only tends to prove this fact; but I will mention one experiment, to fhew that founds affect them much, and is one of their guards, as it is in other animals. In the year 1762, when I was in Portugal, I obferved in a nobleman's garden, near Lifbon, a fmall fifh-pond, full of different kinds of fifh. Its bottom was level with the ground, and was made by forming a bank all round. There was a fhrubbery clofe to it. Whilft I was lying on the bank, obferving the filh The turtle and the crocodile have a structure fomewhat fimilar to this; and the intention is the fame, for their skulls make no part of the organ. This chalky fubitance is alfo found in the ears of amphibious animals, fh fwimming about, I defired a gentleman, who was with me, to take a loaded gun, and go behind the fhrubs and fire it. The reafon for going behind the fhrubs was, that there might not be the leaft reflection of light. The instant the report was made, the fish appeared to be all of one mind, for they vanished inftantaneously into the mud at the bottom, raifing as it were a cloud of mud. In about five minutes after they began to appear, till the whole came forth again. A MICROSCOPIC DESCRIPTION OF THE EYES OF THE MONOCULUS POLYPHEMUS LINNÆI. TH BY MR. WILLIAM ANDRE, SURGEON. HE wonderful structure of the eyes of infects in general, moft commonly illustrated by that of the Libellula, or Dragon-fly, cannot fail of ftriking with attonithment the naturalift who investigates the works of the Great Creator in his most minute productions. According to Lewenhoek, Hook, and others, the carnea of moft infects are made up of an infinite number of fmall, tranfparent, horny lenfes, each refembling, in fome degree, a fmall magnifying glafs. This ftructure prevails in the cornee of infects in general; but the Monoculus Polyphemus, or King Crab, is, among others, an exception to this rule. The Monoculus Polyphemus, or King Crab, is a cruftaceous animal found in all the feas furrounding the continent of America and the West-India islands, and which frequently grows to a very large fize*. I fhall describe so much of the Monoculus only as is neceffary to point out the fituation of the eyes, which have been looked upon as two in number onlyt, though in reality they are four. The largest piece of the cruftaceous covering of this animal, when feparated from the reft of the fhell, has very much the shape of a barber's bafon, or the fore-part of a woman's bonnet. The eyes are a part of the fhell, or, as Linnæus expreffes it, they are tefte innati. They may be diftinguished by the terms large and fmall, or lateral and interior. If the fhell were divided fairly in half, the large eyes would be nearly in the center of each piece, and the fmall ones on the divided edge, near the fore-part of the fheil. The large eyes are at a great distance from each other; but the fmall ones are clofe together. It will appear hereafter, that the large eyes are made up of a great number of small, tranfparent, amber-like cones, and that the fmall ones are compofed of one fuch cone only; fo that they may be divided into eyes with many cones, and eyes with a fingle cone. The large eyes, or thofe with many cones, appear as two tranfparent spots about the fize and nearly of the shape of a kidney bean, the concave edges looking towards each other, and the convex towards the edge of the fhell. If they be examined attentively, we may difcern on their furface a number of small depreffions, which point out the center of each cone. The fmall eyes, or those with a fingle cone, look like too small tranfparent fpots, not larger than a pin's head; thefe, from their minutenefs, are eafily overlooked. The appearances which I have defcribed may be feen on the external furface of the shell with the naked eye; but in order to proceed to a further inveftigation of the fubject, the corned must be removed from the fhell, and applied * Bossu's Travels, vol. 1. p. 368. + LINNAI Syftema Naturæ, tom. I. p. 1057. This being the cafe, the eyes can enjoy no motion; in which particular, as well as in fome others, the Monoculus Polyphemus differs from the genus of crabs, whofe eyes are placed on petioles, or ftalks, and are moveable. The Greek words Aue xoves, and 14070s naves, would express the fenfe in a more concife manner. Oculi palyconici et aculi monocanici, |
