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concutitur, licet deinde idem was absolue ulteriori cumulatione tantum contineat electricitatis, ut more consueto evacuatum pectus valide ferire possit. Aucta tubi capacitate, magis transit, usque dum ita increverit, ut plenarium transitum permittat, nec impedit aquae quantitas justo major, quod testantur commotiones per lacus et flumina propagatae. Conveniunt itaque aqua et glacies in co, quod parvae quantitates concussionem agre tramittant.

Hinc suspicatus sum magnam glaciei quantitatem faciliorem concedere transitum, quod etiam experientia comprobavit, etsi adhuc non majus adhibui frustum quam quo commotio flexuram cubitus attigit. Praeterea ex æqualibus aquae et glaciei quantitatibus, glacies minus transmittit.

No. VI.
LETTER FROM M. DUBOURG TO M. DE LOR."

Parallel between the Theories of Franklin and JNollet.

SiR,

I return you the History of Electricity, which you had the goodness to lend me, with my thanks for it. Mr. Priestley's zeal for the glory of Mr. Franklin has given umbrage to the editor, who is animated with a zeal no less ardent for the memory of the Abbé Nollet. Which would all be very well, if he did not attempt to make it a party matter between the French and English. Let us leave these national prejudices to the common people; let political ministers espouse their passions, if they think they can make them subservient to their designs; but let not philosophers be influenced by these petty local considerations. The republic of letters is one; let us have a care that we do not dismember it; it allows distinctions, but abhors a division. Nollet, Franklin, Hawksbee, Musschenbroek, AEpinus, Wilson, and Beccaria are all fellow-citizens, and we should regard them all with equal favor.

I will give you candidly, and I would repeat it with the same frankness before all the world, my opinion of Franklin and of

* Translated from M. Dubourg's edition of Franklin's works. M. de Lor was Professor of Experimental Philosophy in Paris.-Editor.

Nollet; and I will thank you to weigh my thoughts on this subject, with the same candor and impartiality. Electricity is like an extensive and valuable field, which, after having lain fallow for a long succession of ages, has, for the last few years, been cultivated with wonderful ardor and success, but has not yielded its richest fruits. Natural philosophers of all countries have devoted themselves, in emulation of each other, to electrical researches; they have collected observations, have multiplied and varied experiments; they have constructed systems to explain facts, and to discover their causes; they have attempted to make useful applications of them; but all have not been equally skilful, nor equally successful. It is not for me to decide among them, but every one may say what he thinks. I shall use this right, while I endeavour not to abuse it. And I think we should set out with this principle; of two hypotheses, the best, in my opinion, is that which, embracing all known facts, and showing their agreement and their points of difference, connects them together in such a regular order, that it is not only easy to apprehend all their relations to each other, but that we perceive, almost at the same moment, what is wanting to their completeness, and what remains to be done to fill up some blank spaces, or unite the scattered links in the great chain of philosophical truths. If one would judge, by this standard, Nollet's hypothesis of simultaneous afflux and efflux, and Franklin's hypothesis of positive and negative electricity, I think he would not hesitate long between them. Nollet, by referring every thing vaguely and indistinctly to afflux and efflux, does not teach us to discriminate anything; still less, to foresee any thing. He presents a rallying-point for all facts known, or hereafter to be known, but furnishes no clue to guide us out of the labyrinth where they are to be sought. It is as if a botanist should rest satisfied with telling us, that all trees have a trunk, roots, branches, leaves, flowers, and fruits, without teaching us by what features we may recognise such or such a tree, and in what its distinguishing characteristics consist; facts with which it would be more important, however, to make us acquainted, than tediously to repeat these same generalities respecting each individual. Franklin, in distinguishing between positive and negative elec. tricity, and assigning to each its right place and proper character, so far as the present state of philosophical science admits, diffuses

light far and near, points out the path we must follow in order to make new discoveries, connect them with those already made, extend the limits of science, and make it productive not merely of pleasure but of positive utility. He says ; Do this, and such results will follow; change such a circumstance, and such will be the consequences; thus, you can turn such a thing to account; and thus, you may guard against such an inconvenience. You follow his instructions, and every thing takes place in the manner and order that he has pointed out, every thing answers to his views in Europe as in America, and every thing, even the celestial phenomena, de. monstrate the soundness of principles, which his modesty suffered him to propose only as mere conjectures.

In a word, I think you will find, as I have done, about the same difference between the theories of these two celebrated electricians, as between the barren and fruitful fig-tree.

On the other hand, it must be admitted, to the honor of the Abbé Nollet, that his electrical experiments on organized bodies, and especially with regard to vegetation and transpiration, are very clear and interesting; and that in this department no one has hitherto surpassed or even equalled him. It were much to be wished, that some good natural philosopher, treading in his steps with the same ardor and skill, would devote himself earnestly to the task of making the most brilliant electrical experiments serve to throw light on various other important points in the animal economy, and especially on the nervous system, the glandular system, the circulation of the fluids, muscular motion, respiration, &c., not only as respects man, but, more particularly, animals of different kinds and orders, (quadrupeds, birds, fishes, reptiles, insects, &c.,) directing electricity by turns on the different organic parts, and under every imaginable variety of circumstances. I should especially desire, that some one would make the experiment, and take all possible care to ascertain, whether, while the internal parts are true conductors, the integuments, at least in most animals, (wool, silk, scales, &c.,) are non-conductors, and to what extent; and whether in this respect, there is much difference, or little, between claws and horns, between hair and wool, &c. I am, Sir, &c.

DUBOURG.

END OF VOL. V.

CAMBRIDGE:
FOLSOM, WELLS, AND THURSTON,

PRINTERS TO THE UNIVERSITY.

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