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Istituto Lombardo
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Notes III (a) I discussed this, and reduced the matter to the proper terms of comparison as much as I could, in a Memoir Sulla capacità de’ conduttori elettrici, e sulla commozione, che anche un semplice conduttore è atto a dare, eguale a quella della boccia di Leyden (On the capacity of electric conductors and on the stimulation that even a simple conductor can produce, equal to that of the Leyden jar), which was included in the Opuscoli Scelti (Selected Pamphlets) of Milan, Tom. 1, P. IV and V, 1778, and in the Journal de Physique, Tom. XIII, P. 1, April 1779. It seemed to me then, I had discovered that the capacity of Leyden jars and of Franklin’s panels corresponded, for every square inch of armature, to that that is about six feet long of a cylindrical conductor with a diameter of half an inch and also bigger (since the thickness of conductors, as I show here, contributes very little to their capacity, i.e. much less than their length). So I discovered that the capacity was more or less equal for a flask with 16 square inches of armature and a conductor made of several silver-plated wooden sticks of about half an inch in diameter and 96 feet long, since I realised they both produced the same shaking in the arms. However, the jar was not one of the best since it was made of a glass which was a bit too thick. With other flasks made of thinner glass, which were of greater capacity, of an excellent quality and recently prepared, I found out that they contain, for every square inch of armature, as much electric charge as a cylindrical conductor of an inch in diameter and that is not just 6 feet long but rather 8, 10 feet and even more. (b) Memoirs sull’Elettroforo, sul Condensatore, sulla Capacità de’ Conduttori ecc. (on the "Electrophorus", the Condenser, the Capacity of Conductors, etc.); Letters sulla Meteorologia elettrica (on Electric Meteorology). In the Opuscoli scelti (selected Pamphlets), in Rozier’s Giornale (Journal), in the Biblioteca Fisica (Physics Library) etc.. (c) Principles of Electricity, London, 1779 (d) I do not want to subtract anything from the merit of that excellent author nor do I mean that his experiments should not be taken into consideration, partially or at all. They are marvellous in their own way; and what is more, they led him to the great, fabulous discovery of innate animal electricity, which is typical of the organs and is excellently discussed in the 3rd part of his Works themselves. I have also tried to praise as is due, and I did it in the previous Discourse with as much courtesy as possible. In the meantime, the positive aspect of this 3rd part of Galvani’s Works, which include said great discovery, would remain always intact and unchanged, even though the other parts were entirely cut away, as if they could be considered useless. They are not useless, of course, since they have positive aspects, too. (e) The power of this natural atmospheric electricity on the animal economy and on vegetation has been exaggerated too much. It would be too much to support the idea that its influence on organised bodies is completely absent. However, it can be really said that it is so small that it might hardly be taken into consideration. Even though this electricity is powerful up in the clouds, and extremely powerful in stormy clouds, it is not sensitive any more when it is only a few feet from the ground, also in places without walls or plants, so that, usually the most precise electroscopes give just a few signs of it, when placed as high as our heads. When it affects these instruments, moving them by 6, 8, 10 degrees or more, and this happens very rarely, it is, however, nothing but pressure electricity, which does not pass to underlying bodies, or at least does so only very slowly. So, what effect, what change will such feeble electricity be able to produce in organic bodies? It is easy to judge, using as a term of comparison artificial electricity, which is a bit more lively, and also pressure electricity that gives no sensitive changes. Oh! If only things could always be reduced to their proper value, how many effects would no longer be attributed to inadequate causes, and if they were examined once again a lot of effects could be explained with other principles. (See my already mentioned Lettere sulla Meteorologia elettrica [Letters on electric Meteorology], particularly a long note, the 4th one). (f) Among numerous Works on the application of electricity in Medicine, the most complete, rational, far from both the excesses of fanatics and visionaries, and from intemperate Pyrrhonism, the most erudite and judicious one is the following: De l’application de l’electricité à la physique et à la medicine par A. PAETS van TROOSTWYK et C.R.T. KRAYENHOFF, Amsterdam, 1788. (g) I would have liked to show here the figures that I have drawn, but there has not been enough time to prepare for copper etching. Luckily, even without figures, the readers can easily imagine this instrument and build a similar one, if they wish to repeat my experiments. (h)II have notably improved this electrometer. The improvements are indicated in the Lettere sulla Meteorologia elettrica (Letters on electric Meteorology) (first letter) already mentioned many times. (i) See Lett. cit., 1st lett.(l) See cit. Lett., 1st lett. (m) Since my long, thin straw micro-electrometers do not go up to 30 degrees, but rather to 20 or 24 maximum. Beyond that level, such pendulums are brought to touch the surfaces of the flask. In that case, I will use another electrometer with shorter, thicker straws such that each of its degrees corresponds to 4 degrees of the first one and to ¼ of degree of the Quad. el. (n) It has been included in the previous Quad. of this Journal. See pp. 129-130. (o) See the same Vol., p. 175 et seq. (q) A lot of examples could be given about this, but two of them will suffice. The first is taken from electricity, too. What did both Physicists and Physicians expect, many years ago, from artificial electricity applied to Medicine? In the end, Medicine owes so little to this medical Electricity that it has almost been abandoned! The same happened with the discovery of the instruments with which it was possible to measure the respirability of different airs. The intention was to use the so-called Eudiometers to know every degree of pollution and quality, to distinguish all diseased airs, etc., when, actually by means of said instruments, it was possible to measure only one of the numerous features and modifications to which atmospheric air is susceptible. So, the degrees of its respirability, or rather the amount of vital pure air present, could be measured. (About this matter, you might see the eudiometer article which I myself wrote, and included within the translation by SCOPOLI of the Dizionario di chimica (Dictionary of Chemistry), by MACQUER). Not for these results, which often forced people to reformulate interesting and complex concepts and to lower sails and renounce an adventurous voyage, should the courageous attempts and efforts made by men of genius be condemned. Attempts and efforts are made in order to extend any discovery and to apply it to as many fields as possible. It is better, however, that, first of all, intelligence be employed to search for and experiment with all possible applications, even pushing things beyond their limits, though we must be ready to withdraw then, whenever we realise we have gone too far into the matter, and finally give the proper value to each event and result. (r) Mr. Galvani once again noticed that the diversity of the metals has a strong influence, so that convulsions occur easily and more violently, if iron or brass is the one to touch the muscles, while tin or silver is the other that touches the nerves of the frog which prepared according to his method. "Illud praeterea (this is what he writes on p. 21) peculiare atque animadversione dignum, languentibus potissimum praeparatorum animalium viribus, circa conductores arcus aut deferentia plana contingit nobis saepissime observare, variam nempe eorum ac multiplicem metallicam substantiam cum ad obtinendas, tum ad augendas contractiones musculares multum posse, et quidem longe magis, quam una eademque metallica substantia. Ita ex. gr. Si arcus totus ferreus fuerit, aut ferreus uncus, et ferreum item planum deferens, saepe saepius aut deficient contractiones, aut erunt perexiguae. Si vero eorum alterum ferreum ex. gr. Fuerit, aereum alterum, multo magis si argenteum (argenteum enim prae caeteris metallis ad deferendam animalem electricitatem visum est nobis idoneum) contractiones ut plurimus longe majores contingant, quam si uno eodemque metallo, ac folio, argento licet, fuerit uterque locu obductus, seu ut inquiunt armatus": The same concepts are repeated by the praised author in other excerpts from his Works. His observations and mine are equal, therefore, except that I noticed a further element: if in the animal that has been prepared according to Galvani’s method, convulsions are less intense and often missing when the armatures are of the same metal, in the animal that I left intact in my way, with uncovered muscles and covered nerves, convulsions are completely lacking. If some little movement is obtained, this means that probably the metals are slightly different even though they have the same name and they differ because of some different alloy or because they are more or less hammered and compact, or because their surfaces are extremely different, one of them being more or less smooth and clean. I then tried to understand better which diversity is more favourable to conducting the experiment, successfully, i.e. to exciting stronger convulsions in the animal more easily. I found out that such metals can be conveniently divided into three ranks, putting tin and lead in the bottom one, iron, copper, brass in the middle one, mercury, gold, silver and platinum in the uppermost one. The best solution, therefore, is the one that opposes a metal of the top rank (i.e. gold but above all silver) to one of the bottom rank (i.e. lead or tin). The metals belonging to the middle rank, iron and brass, give fairly good results if they are opposed to tin and lead, but such results are worse than the ones obtained with gold and silver and even worse are the results if they are opposed to the latter ones. This is because iron, brass and copper, which we put in the middle rank, are much closer to the top rank than to the bottom one. In the latter there remain exclusively, alone and separated by a big interval, the two soft metals, lead and tin. I have not determined yet the little differences among the metals of the same rank, like between silver and gold, iron and brass; and I have not fixed the proper rank for the other metals, the so-called semi-metals, that is for zinc, antimony, bismuth, etc.. I will talk about such research, which is not, however, of major importance, when the time comes. See Memoir I, which was included in T. II 2° Quad. of this Giornale Fisico (Physical Journal); and also my short article addressed to Dr. BARONIO, which comes before it. I have now extended this experiment also to big animals, Rams, Calves, etc., and the results are as successful as with small and middle-size animals. This is the case with eels and snakes. Since in various worms and insects the direction of the nerves and of the muscles is transverse and circular rather than longitudinal, i.e. restricted over most of it within the borders of certain strips or rings, it is easy to understand why in eels the two armatures have to be correspondent and close for muscular contractions to occur. See § 72 and the note thereon. Translator’s note: Cav. is nowadays a Distinguished Service Order recognised in Italy and approximately equivalent to the British knighthood. It could be rendered more correctly by Professor Sir Alessandro Volta. At this stage, Volta had not yet been ennobled by Napoleon to the status of Count, so Cavaliere is another title of respect, like Don.
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