well fed indeed juft three or four hours before the experiment, is fixed upon a table: its abdomen is opened, while it is yet alive, and a ligature is paffed round its mefenteric veffels, as near the root of the mefentery as poffible.-But we will not ftain our page any further. The calls of hunger, and other confiderations, reconcile men to the killing of animals for food: but the philofobical hunger of the anatomift or phyfiologift, however craving, furely gives him no right to torture them; particularly in cafes where the profpect of utility, to fay the beft of it, is exceedingly diftant and problematical. What myriads of innocent brutes have experienced all poffible kinds and degrees of torture, in order that the various fenfibility and irritability of the different parts of animal bodies might be afcertained by phyfiologifts; who, while they were cutting, vellicating, and burning the nerves of brutes, feem intirely to have forgot that they had any ! So infatiable and encroaching is this fcientific appetite, that we fometimes think it is happy for us all that the laws protect the mefenteries of his majesty's good fubjects from the knives, hooks, and ligatures of these keen inquirers; who, no doubt, frequently caft a wifhful eye towards our abdomens, and long to be exercifing their scalpels and pincers on their contents +. The lucklefs cur, and the harmlefs goofe, unhappily have no other protection than that which they derive from our knowledge of the feelings which they poffefs congenial to our own, and that fympathetic fenfibility implanted by nature in the human breaft; but which, unfortunately for them, appears to be deadened or totally extinguished in the breasts of thefe inquirers, by the love of fame, the ardor of discovery, and the rage of philofophical curiofity; the most successful efforts of which are never likely to afford an adequate compenfation for the immenfe fums of animal mifery produced by them. + This fufpicion of ours is by no means extravagant, as we could prove from the writings of fome of thefe gentlemen, who have fomewhat incautiously, and rather impolitically, owned how far their curiofity, with regard to certain contefted points, has carried them, even in the human fubject. We shall produce only one inftance: a perfon having had all the tendons of his hand laid bare by accident, Monf. Ffeized the glorious opportunity which prefented itself of trying whether, and how far, the human tendons are fenfible;— a question which has been ftrongly litigated among the phyfiologifts. He pinched the naked tendons with a forceps: he next very nearly perforated them with a probe; and at laft, went fo far as to try the effects of the cauftic oil of vitriol upon them. The patient, doubtJefs, was unacquainted with the drift of these curious manœuvres, and, we are told, did not fuffer from them.-'Twas fortunate :-but furely this was corio humano budere with a vengeance! ART. ART. VII. Experiments and Obfervations on Electricity. Made at Philadelphia in America by Benjamin Franklin, LL. D. F. R.S. To which are added, Letters and Papers on Philofophical Subjects. The whole corrected, methodized, improved, and now first collected into one Volume, and illustrated with Copper-plates. 4to. 10 s. 6d. Henry. 1769. THE HE philofophical papers and letters contained in this excellent collection, and which are, in general, arranged merely in the order of their dates, without regard to the nature of the various fubjects treated in them, may be divided into three claffes. Under the firft we may place the Experiments and Obfervations on Electricity, which are mentioned in the first part of the title, and were originally published, in the form of letters to the late Mr. Collinfon, between the years 1751 and 1754. The philofophical world have been too long acquainted with the merit of thefe juftly celebrated publications to require, at this time, any character of them from us. The light thrown by them on a new and extensive branch of physical science has already diffused itself throughout Europe; where the experiments and obfervations of Dr. Franklin conftitute the principia of electricity, and form the bafis of a fyftem equally fimple and profound. These letters amount to nearly a third part of the work now before us. To this fourth edition the Author has added fome explanatory notes, as well as others, in which, with the moft laudable and fcrupulous punctuality, he fpecifies the particular hints and experiments for which he was indebted to his philofophical affociates in America, whom he names. Thefe acknowledgments, however, are neither numerous or important enough to produce any confiderable diminution of the Author's fame as a philofopher. Under the second clafs we may place a few papers which have been formerly published, either in feparate pamphlets, in the Philofophical Tranfactions, or in different periodical publications. Among thefe is a defcription of the Author's newinvented Penfylvania fire-places,'. firft published by him in Philadelphia in the year 1745. In this excellent paper, after fhewing the difadvantages attending all the methods of warming rooms, then in ufe, the Author particularly defcribes, delineates, and fhews, the advantages of this new construction; by means of which a room is equally warmed in every part of it, at a small expence of fuel, principally by heated air which is continually paffing into it through apertures made in an airbox, or cavity behind the fire, to the amount of near ten barrels in an hour, by eftimation. The air, thus heated, receives no noxious impregnation either from the fuel, or the metal of 04 the the stove; and, as it is continually changed, is preserved sweet and wholesome as well as warm. The Author's obfervations concerning the increase of mankind, the peopling of countries, &c.' which were written in Penfylvania in the year 1751, are here likewife republished; and are followed, in that part of the work which confifts only of original publications, by a letter from a friend on the fame fubject, who, with great acuteness, difcuffes the question, how far the numbers of a people, and their political profperity in general, are influenced by manners and the arts, or by their moral and mechanical habits. The third and last paper which falls under this clafs (we omit the mention of a few papers of less confequence) is intitled, Phyfical and meteorological obfervations, conjectures, and fuppofitions. We fhould dwell with pleasure on this collection of philofophical aphorifms, on the nature and cause of evaporation, the production of winds, &c. had it not, fome years ago, been prefented to the public in the 55th volume of the Philofophical Tranfactions for the year 1765. The remaining papers and letters, which conftitute the largest half of this volume, are now publifhed for the first time, and are the fruits of the Author's correfpondence with feveral of his ingenious friends, on a great variety of philofophical fubjects. A few indeed of the letters were read fome years ago, at different meetings of the Royal Society; but the Author having particularly requested that they might not be printed, none of them were inferted in the Tranfactions, as he had, at that time, formed a design of revising them, and of pursuing fome of the inquiries farther. Finding, however, no likelihood of having fufficient leifure for that purpofe, he has at length,' as we are told in a note, been induced, imperfect as they are, to permit their publication; as fome of the hints they contain may poffibly be useful to others in their philofophical refearches.-There are not many philofophical writers, we aphend, who can fuffer fo little by appearing in an undress before the public, as our Author. In the fame artlefs, unaffected garb were his first and great difcoveries in electricity prefented to the philofophical world, who will receive the most imperfect fuggeftions, or even the whimfies of genius, if fuch are to be found in this work, with pleasure, efpecially when they are prefented in the fimple, familiar, and unaffuming manner fo peculiar to Dr. Franklin. Out of the great variety of curious matter contained in this work, we shall first felect, and take particular notice of, fome propofed improvements of the Author's apparatus for preserving buildings from the danger of lightning. Thefe improvements have been principally indicated by fome phænomena which have been been obferved in houfes furnished with rods for this purpose, on which the lightning has fallen. In the conftruction of an inftrument fo new, and of which we could have fo little experience, it is rather lucky, the Author obferves, that we fhould, at first, be fo near the truth as we feem to be, and commit fo few errors.' We fhall collect and abridge, from the different parts of this work, the most effential particulars relating to this fubject, fo interefting to electricians and philofophers, and which too may be thought a matter of no small importance, by many who do not confider it in a philofophical view for although, to use the Author's own words, the mischiefs done by lightning are not so frequent here' as in America, and though those who calculate chances may perhaps find that one death (or the deftruction of one house) in a hundred thousand happens from that cause, and that therefore it is scarce worth while to be at any expence to guard against it ;yet, in all countries, there are particular fituations of buildings more expofed than others to fuch accidents, and there are minds fo ftrongly impreffed with the apprehenfion of them, as to be very unhappy every time that any thunder is within their hearing-it may therefore be proper to render this little piece of new knowledge as general and as well understood as poffible, fince to make us fafe is not all its advantage; it is fome to make us eafy.' Mr. Weft's house at Philadelphia was evidently fecured from receiving damage by a ftroke of lightning, which melted the point of his conducting rod; gave his clerk, who was leaning against the wall of a parlour, on the outside of which the conductor passed, a smart electric fhock in that part of his body which touched the wall; and was feen diffufing itself over the pavement of the street (which was then wet with rain) to the diftance of two or three yards from the foot of the conductor, the lower end of which was fixed to a ring in the top of an iron ftake that was driven about four or five feet into the earth, which was at that time, the Author fuppofes, very dry underneath the pavement. From this laft circumftance he infers the neceffity of finking the rod deeper, or at least till it comes into contact with water or moift earth, adapted to receive and convey away the electric fluid. The Author gives another reafon for finking the lower end of the rod to a confiderable depth, and also for turning it outwards, under ground, to fome diftance from the foundation, as the water dripping from the eaves, and falling near the foundation, may fometimes foak down fo far as to come near the end of the rod, while the earth furrounding it is dry; for it is now found that by the electric fhock water is exploded or blown into an elastic vapour, by the immense expansive force of which the foundation may be endan gered. gered. Father Beccaria firft made, or at least published, obfervations on the explofion of water, by the action of the electric fluid, which have fince been verified by Dr. Franklin, who fent a charge through an empty glass tube, which fuftained it without injury; but which, being filled with water, was shattered to pieces and driven all about the room, where, however, no traces of the water could be discovered. That it was diffipated into vapour the Author feems to have put out of doubt, by the following curious experiment: he filled a fimilar tube with ink, and placed it on a clean fheet of paper, on which, after the explosion, by which the tube was burst, he could neither find any moisture, nor even the leaft ftain from the ink. Trees have, by lightning, been reduced into fine splinters like a broom; an effect which the Author fuppofes to proceed from the watry fluid contained in their numerous fap veffels being fuddenly expanded into vapour. To the explosion of water, likewise, running or lodging in the joints or cracks in walls, he attributes much of the damage which buildings fometimes fuffer from lightning. Although the Author, in the infancy of this discovery, reafoning from analogy, had fuppofed that even fmall wires might fafely conduct a flash of lightning to the earth; and though Mr. Weft's conductor, formed of nail rods not much above one quarter of an inch thick, conveyed the lightning to the ground, without any other damage than melting two or three inches of the flender, pointed, brafs wire, which terminated the upper part of the apparatus; yet, from fome accounts received from Carolina, and here related, there is reason, he thinks, to presume that larger rods may fometimes be neceffary, at least for the fecurity of the conductor itself, which, when too fmail, may be deftroyed in exe cuting its office, though at the same time it preferves the house.' It appears likewife, from one of these relations, to be an effential circumftance to the perfection of this inftrument, that the rod fhould be perfectly continuous or of one piece, where that is practicable, or, at least, that the ends of each rod fhould be confined in clofe contact with each other, either by fcrews or otherwife. In letter 40th, a very judicious and diftinct account is given by Mr. Mayne of South Carolina, of the effects of a violent flash of lightning on his conducting apparatus, which is accompanied by feveral instructive reflections of the Author. We fhall relate the moft material particulars. Mr. Mayne's rods, which were fixed to the outside of his chimney, appear to have been of a fufficient thicknels, fomewhat above half an inch in diameter; but they were connected to each other only by hooks turned at the ends of each rod, * See Monthly Review, vol. xxxvii. O&. 1767, page 249. the |