in support of his sentiments still farther experiments, some of which, he flatters hi nself, will appear more surprising than any that have already been communicated to the world.

"Let it therefore suffice for the present to say, that even those persons, who happen to differ from him in opinion as to some points, universally acknowledge his great merit, and particularly the learned gentleman, whom I have more than once mentioned, is pleased to declare Mr. Franklin to be a very able and ingenious man,' and says, 'that he has a head to conceive, and a hand to carry into execution, whatever he thinks may conduce to enlighten the subject-matter of which he is treating;' and, although that gentleman 'cannot agree with him in some of his opinions, yet he thinks scarce anybody better acquainted with the subject of electricity than Mr. Franklin.' These testimonials, therefore, given by so ca pable as well as unprejudiced judges, in his favor, and more especially that character of him, which I have just quoted, joined with that opinion, which every one who has read his books must entertain of him, will sufficiently justify your Council in having adjudged to Mr. Franklin the Copley medal for this year, as a mark of distinction due to his unquestionable merit.

"Many and very considerable advantages and improvements have, within the space of some years past, been made in several branches of natural knowledge; but there is ample room still remaining for the inquisitive and able philosopher to employ his skill and labor. The Book of Nature is a very huge and comprehensive volume; and, notwithstanding no small part of it has been unfolded and exposed to our view by learned and ingenious men of this and many other countries, yet it still contains abundantly sufficient matter to exercise our talents upon, and which justly ought to excite our curiosity, and encourage us to proceed with vigor in our endeavours to bring to light what is at present concealed from our eyes. We know that few things are of so occult and obstinate a nature, as not to yield to sagacity, and to be forced to lay open their most hidden properties to the diligent and inquisitive inquirer.

"In confidence whereof let us pursue, with unwearied application and assiduity, our researches into every branch of natural philosophy. Nor let us be discouraged from such pursuits by a mistaken notion, that any part of it is too inconsiderable to deserve our regard and attention; since who could have entertained any hopes, some years ago, that electricity was capable of furnishing matter for so great and important discoveries, as have lately been made in relation thereto, and which a this time afford us a promising pros

pect of much more and greater, f due pains are not wanting, on our part, to search after them?

"It is, therefore, to be hoped, that those gentlemen, who have applied their thoughts and studies to lay open the amazing properties of electricity, will not sit down contented with the progress that has already been made therein, but will rather be encouraged thereby to proceed diligently in the same work. And I flatter myself, that Mr. Franklin will consider this honorable present not only as a reward, in some measure, of the discoveries with which he has already favored the world in relation to this very powerful agent in nature, but also as a proper incitement to carry on still farther his inquiries into this truly deserving and important subject. Nor do I in the least doubt, that our worthy brother, Mr. Peter Collinson, to whom (as Mr. Franklin resides in a remote country) I shall recommend the care of conveying this medal to him, will make use of all proper means to induce him to persevere in so laudable an undertaking." *

In the Minutes of the Council, December. 19th, 1754, it is recorded. “A letter from Benjamin Franklin, Esquire, to the President and Council of the Royal Society, dated Philadelphia, 29 May, 1754, returning his thanks for the honor they have done him in bestowing on him the gold medal for the year 1753, was read."

Franklin was elected a Fellow of the Royal Society on the 29th of April, 1756.- Editor.

No. IV.

LETTER FROM JOHN BAPTIST BECCARIA TO BENJAMIN FRANKLIN.

Experiments in Electricity.

READ AT THE ROYAL SOCIETY, February 14TH, 1760.

Benjamino Franklin, viro de re electrica meritissimo, Joannes Baptista Beccaria ex Scholis Piis S. P. D.

1. SOSPITEM ex America Londinum te appulisse gaudeo, vir præclarissime. Offero tibi de motibus electricis, qualem experimentis excudi, hypothesin; partior hanc in duas partes, quemadmodum ipsa postulare videtur motuum hujusmodi differentia; ago parte prima de accessionibus, de discessionibus dico parte altera.

2. Et continuo universam de accessionibus pertractationem meam ita paucis comprehendo; "Quum ignis electricus copiosior in corpore altero vi expandendi se ad æqualitatem trajicit in alterum, partem interjecti aeris dimovet e loco pro majore sua copia majorem; fit inde, ut aer a tergo corporibus adjacens deficiente fulcro aeris intermedii ruat versus ipsum medium locum; ruit vero non circumeundo corpora, quæ via est longior, atque impedita abs igne profluente, sed ipsa trudendo a tergo; hac aeris trusione accedunt corpora inæqualiter electrica; dum accedunt, accelerantur, quia pro accessione majore copiosior ignis interfluit, copiosior intermedius aer disjicitur, augeturque adeo momentum aeris a tergo trudentis."

EXPERIMENTUM 1.

3. Aerem disjici ab interfluente electrico igne, scintillæ experimento demonstratur, quæ excitatur in medio tubulo, hinc clauso hermetice, inde impedito abs liquore aliquo, ipsa enim, disjiciens liquorem, disjectum aerem testatur.

4. Neque vero interfluens ignis aeris intermedii disjecti fulcrum potest supplere, quo aer corporibus a tergo adjacens sustineatur; is enim liberrime effluit, et effunditur per alterum corpus; quare, cum non fulciatur ipse, nec fulcri vices potest agere.

EXPERIMENTUM II.

5. Experimento res confirmatur plane luculentissimo; vittam ex charta inaurata longam pollices octo, latam lineas quatuor, convolvo

circe sese ut cylindrum solidum D efformet; hunc suspendo serico filo D, G, sub fornice vitri pneumatici I, H, K, per cujus verticem

H init virga metallica B, C, desinens in metallicam sphæram C; figo in lance I, K, virgam metallicam L, E, simili sphæra ornatam; nempe sphæræ C et E sunt in eodem plano cum pendulo D, atque ab ipso distant ambæ æqualiter; tum nexa catena A, B, quæ pertinet ad machinam electricam, virga B, C, et consequenter immisso electrico igne in virgam B, C, observo; 1. ante subductum aerem chartaceum cylindrum D agitari vehementissimis vibrationibus inter duas sphæras E, C; 2. dum aer subducitur, minui eam agitationem plane pro copia subducti aeris; 3. omni, quantus potest, aere subducto, cylindrum D vix nutare. His observatis aerem restituo par ticulatim; atque pro aere admisso video vibrationes iterum augescere, et fieri, quemadmodum antea, vehementissimas; quæ dum contemplor singula, atque omnia simul comprehendo animo, intelligo magnitudinem motuum electricorum aeri, vel toti, vel residuo proportione respondere.

EXPERIMENTUM III.

6 Quod leviora corpuscula, bracteolæ, et pulvisculi, motu adhuc satis sensili agitentur in rarefacto aere, id in causa fuit, cur censuerim a principio cum physicis aliis electricos motus actioni ignis electrici in aerem acceptos referri non debere; quod, re nunc accuratius collata, residuos videam in residuo aere motus non majorem habere ad primos motus, qui fiunt in toto aere atmospherico,

proportionem, quam ea sit, quæ inter residuum et primum aerem intercedit, id nunc facit, ut illum meum, et alienum errorem agnoscam, atque in contrariam veniam, quam verissima testatur experientia, sententiam.

7. Neque omittam partem observationis opportunissimam rei confirmanda; soleo enim allatum ultimo loco experimentum persæpe capere in cubiculo obtenebrato, atque tum observo ignem vibrantem pendulum ante aerem subductum micare hinc inde crepitanibus quidem, ac lucidissimis, sed arctis, atque brevibus prope sphæram utramque scintillis; deinceps ignem hunc pro subducto aere, adeoque pro minutis penduli vibrationibus effluere magis amplo radio, magis tranquillo, magis continuo, quanquam non ita micante.

8. Atque hæc ipsa res certe reactionem aeris demonstrat ignem electricum cohibentis in densitate quadam, quæ densitati suæ proportioni respondeat; hæc autem aeris reactio non potest actioni non respondere ignis electrici aerem nitentis disjicere, ac plane disjicientis, ubi necessaria is igni vi polleat.

9. Atque his plura non adferam tibi pro accessionibus explicandis corporum electricorum inæqualiter, attuli in datis ad Beccarium litteris, in quibus tamen non nisi dubitanter plura admodum disserebam de mechanica accessionum causa; accuratior consideratio experimentorum facit nunc, ut de accessionum causa dicam fidentius.

10. Corpora æqualiter electrica discedunt; qua causa id efficiatur, nunc persequar.

11. "Ignis electricus, qui quoquomodo insidet in corporibus, nititur, ut libretur cum igne electrico, qui insidet in aere. Si uterque (sinito me illum deinceps proprium dicere hunc aereum) "æqualem habet proportionem ad nativam corporum atque aeris capacitatem, corpora accedunt, aut in nativa quiescunt directione; alter si superat proprius, vel aereus, corpora explicat similiter, compel litque ad discessionem." Hæc rei narratio.

EXPERIMENTUM IV.

12. Quoties in cubiculo quodam meo amplo ipso quidem at clauso pergo diutius urgere alium atque alium in catenam electricum ignem, experior partem ejus ignis effundi in aerem ambientem, ipsumque etiam, quantuscumque in cubiculo est (dum a tempestate siccus sit, vel abs igne) facere excessu electricum. Duo enim tenuia ex lino fila, quæ vel summis digitis prehensa, vel arundine suspensa defero quolibet, in quodlibet cubiculi spatium, mutuo