Abbildungen der Seite


Conductors of Lightning. - Project of the Royal So

ciety to ascertain the Attraction of Mountains. Volcanic Eruptions. - Experiments on the Torpedo.

[ocr errors]


Naples, 23 February, 1773. SIR, I have received with the greatest pleasure the two letters, which you did me the honor to write to me; the one of October 8th, the other of December 1st. As they were both addressed to me at Geneva, and as I left that place in the beginning of October to come to Italy to pass the winter, they reached me very late, and I have thus been debarred the privilege of showing you by a prompt reply, how much I feel flattered by the honor of your correspondence. The letter on the action of pointed conductors, and the accompanying Essay, contain experiments and reasonings perfectly conclusive, and which leave no doubt as to the utility of these ingenious preservatives.t

If I had been acquainted with these new experiments, I should have made use of them with great advantage, in a short apologetic memoir, which I published in October, 1771, for the information of some people, who were terrified at a conductor, which I had erected at Geneva before the house I lived in. This Memoir, however, met with the desired success. It

* M. De Saussure was the well-known professor at Geneva, celebrated throughout Europe for his philosophical writings, and particularly for his interesting account of his ascent of Mont Blanc. - Editor.

† Franklin's letters to M. de Saussure have not been preserved. The papers here alluded to were probably in part those relating to the powe der magazines at Purfleet. See Vol. V. pp. 427 – 445. — EDITOR.

[ocr errors]
[ocr errors]


reassured everybody, and I had the pleasure of watching the electricity from the clouds during the whole course of the last summer. Several persons even followed this example, and raised conductors either upon their houses or before them. M. de Voltaire was one of the first. He does the same justice to your theory, that he did to that of the immortal Newton.

The project of the Royal Society is well worthy of the zeal of that illustrious body for the advancement of useful knowledge; and I should be much pleased, if I could in any way aid them in the execution of this project.* Had I been at Geneva, I should have made it my duty and pleasure to take a journey to the mountains in the neighbourhood, to ascertain with precision the dimensions of the mountains and valleys, which I thought best suited for the execution of this design. I do not believe, however, that, among those with which I am acquainted, there is any place exactly suited to give certain information on the subject, to which their researches are directed. In the Jura, there is no summit sufficiently high, since the Dole, the mountain which rises highest above the level of our lake, does not reach seven hundred toises above this level.

Then it must be considered that the Jura, as well as the Alps, form continued chains of mountains, all

* The Royal Society had recently engaged in the project of ascertaining the lateral attraction of mountains, with the view of determining the mean density of the earth upon the Newtonian theory of gravitation. On this subject, it would seem, Dr. Franklin had written to request the aid of M. de Saussure, who had bestowed much time and attention in observing the geological structure and formation of the mountains of the Alps. The object of the Society was finally attained by Dr. Maskelyne, the Astronomer Royal, who made a series of observations on the Schihallion Mountain, in Perthshire, which were considered conclusive. He received the Copley Medal from the Royal Society, for this successful enterprise, on the 30th of November, 1775. See Sir John PRINGLE's Six Discourses, p. 93. - EDITOR.

connected together, or, at least, situated at very short distances from each other. There is no single mountain, or, at least, I know of none, of sufficient height. You often find deep valleys, surrounded by high mountains, but behind these mountains are other valleys and other mountains, so that the deviations which might be observed in the plumb-line, would be the complex effect of the combined attractions of all these mountains; and, in order to deduce from them a comparison between the density of the earth and that of these mountains, much labor and many calculations would be required. As far as I am able to judge, it appears to me that some large rock, rising out of the open sea, like the Peak of Teneriffe, would be the most suitable place for this attempt.

The memoir upon this subject, which you did me the honor to send, I have transmitted to Lord Stanhope, at Geneva, that he may confer respecting it with M. de Luc, who, having attended particularly to the height of mountains, in connexion with his observations of the barometer, is the best man in the world to give valuable information on this subject. It is now, doubtless, well known that Signor Beccaria of Turin, who has measured a degree of the meridian at the foot of the Alps, has had an opportunity to observe great deviations of the plumb-line, and would thus be enabled to furnish useful hints to the Royal Society.

I have the pleasure of often seeing here Sir William Hamilton, who has the kindness to take me to the most interesting places in the neighbourhood of Naples, those which establish his theory of volcanoes ancient and modern, and prove that the whole Bay of Naples, from the sea to the Apennines, has been thrown up from the bottom of the sea by subterranean fires, and is thus the product of volcanoes rather than the theatre



of their ravages. We are also much devoted to electricity. The little machine, which Mr. Nairne made for him, is really excellent, and much the best they have ever had in this part of Italy. Sir William Hamilton, knowing that I had the honor of writing to you, has requested me to present his compliments.

I regret extremely that I was not at Geneva to receive M. de Normandy. I should have been delighted to have had this opportunity to prove to you how highly I value your recommendation. If you have any commands for me in Naples, I shall still be able to receive them here, and you may address them to Sir William Hamilton. We propose to try together some experiments on the electricity of the vapours of Vesuvius, although, to say the truth, I regard them merely as conductors, which establish a communication between the earth and the higher regions of the atmosphere.

Sir William Hamilton has also done me the kindness to invite me to witness some experiments he has tried with the Torpedo. These experiments are not decisive, because the fishes we had were small, and gave only slight shocks, but no sign whatever of electricity appeared. We are waiting for some larger ones, in order to continue this investigation, according to the mode which you have yourself marked out.*

Accept my assurances of the high consideration and esteem, with which I have the honor to be,

Sir, &c.


• See the rules given by Dr. Franklin on this subject, Vol. V. p. 412. Also a letter from Mr. Walsh above, p. 348. - EDITOR.


Dr. Priestley. Effects of Lightning.

Cambridge, New England, 4 March, 1773. DEAR SIR, I received your favor of September 18th. I return you many thanks for Dr. Priestley's piece on impregnațing water with fixed air. If this should prove an effectual remedy for the sea-scurvy, it would be indeed a most important discovery. I am extremely concerned to hear that Dr. Priestley is so poorly provided for, while so many are rolling about here in gilt chariots, with very ample stipends. I admire his comprehensive genius, his perspicuity and vigor of composition, his indefatigable application, and his free, independent spirit, and wish it were in my power to do him any kind of service. It would give me great pleasure to see him well settled in America; though indeed I am inclined to think he can prosecute his learned labors to greater advantage in England. A man of his abilities would do honor to any of the colleges. At present there is no vacancy among them; but if there were, I believe, Sir, you judge perfectly right, that his religious principles would hardly be thought orthodox enough. Indeed, I doubt, whether they would do at the Rhode Island College, any more than in the others. That college is entirely in the hands of the Baptists, and intended to continue so, and I never understood that Dr. Priestley was of their persuasion. However, I cannot but hope that his great and just reputation will procure something valuable for him, and adequate to his merit.

I have looked over his treatise of Optics, which you were so good as to present to our library, with great

« ZurückWeiter »