I am sorry you could not see Mr. Kinnersley's Lectures; they would have pleased you. I send you Mr. Wilson's book, which I just received from London, and think it contains the best directions for the use of the machine, that are extant. When you have done

with it, please to return it to, Dear Sir,

Your most humble servant,

B. FRANKLIN.

FROM CADWALLADER COLDEN TO B. FRANKLIN.

Cause of the Cohesion of the Particles of Matter. Concerning a Translation of a German Writer's Remarks on Mr. Colden's Philosophical Principles.

Coldenham, 24 October, 1752.

DEAR SIR, I now send back to you Wilson's Electricity, for the use of which I am much obliged. My youngest son, the only one I have with me, hopes to be able to make electrical experiments tolerably well. Mr. Wilson, I think, is on the true scent of the cause of electricity, though it be plain he is not sufficiently informed of the nature of that elastic fluid, which he calls ether, to be able sufficiently to account for the phenomena. In my opinion, some more perfect knowledge of the air, than we have is likewise necessary, and the cause of the cohesion of the parts of bodies, which last has been lately the subject of my meditations. No tolerable account of this, so far as I know, has been given by any philosopher; and, if this can be accounted for from my principles, it will go a great way to confirm them. I hope to let you see something on this head.

At present, I shall only mention one theorem, viz. that the parts or particles of bodies are at a great distance from each other in the ratio of their bulk. To prove this, it is supposed that the solid particles of inert matter are impenetrable by light, or that light cannot be in the same space with matter. Then, since light freely passes through pellucid bodies in straight lines, and in all directions, with a very small diminution of its quantity, the distance between the particles of pellucid bodies must be very great in proportion to their bulk, if the prodigious number of those particles be considered, which must be in a pellucid body of any bulk. This may be easily conceived, by placing a number of points in any order, and considering how they must stop the progress of light in many directions. Again, the number of particles in the same quantity of space in several bodies is as their specific gravity. Now, considering the difference of specific gravity of pellucid bodies, and of any other opaque body, and that it does not arise to a great degree, the parts of all bodies must be at a great distance from each other in proportion to their bulk. Sir Isaac Newton accounts for the cohesion of the parts of bodies, from the stronger attraction in little bodies than in great bodies; but, if this were the cause, the parts of bodies must move together into mutual contact, if some other power do not keep them separated. What I call ether is essentially different from Mr. Wilson's ether, and from that elastic fluid, which I think produces electrical phenomena. Sir Isaac Newton was far from having clear conceptions of what I call ether; though he perceived from the phenomena that some such medium must exist between the several bodies in the universe, and within them between their component parts.

I have at last got the Remarks on the first causes

of action in matter well translated by Mr. Harwich, a Lutheran minister, who is well acquainted with the German systems of philosophy, and thereby more capable of making a good translation. I have likewise drawn up an Answer to the Remarks, which I expect may assist you to form a better conception of my principles, and of the truth of them, than what you have already seen. I now send both the Remarks and Answer to Mr. Alexander, and I shall desire him to transmit them to you, if he do not think it necessary to alter any thing in the Answer. In the mean time, I send you the original Remarks in the German language, that you may better judge of the translation when you shall see it.

The Remarks and Answer are chiefly on the metaphysical part of my system. The same subject is treated of in Dr. Johnson's Noëtica,* but in a very different manner. I hope from your friendship, that you will give your sentiments without reserve; and I beg that you will take some pains, because I have some distant prospect of being able to explain the phenomena of electricity from my principles, with your assistIf this can be done, I am persuaded that the

ance.

A treatise entitled, “Noëtica; or the First Principles of Human Knowledge." The author, Dr. Samuel Johnson, was a clergyman of the Episcopal Church, and the first President of King's College in New York. He was distinguished as a scholar, a writer, and a divine. The above work treats of metaphysics and logic, and is remarkable for the clearness of its method, and the acuteness with which some of the difficult topics in mental philosophy are discussed. It was followed by a treatise called "Ethica; or the First Principles of Moral Philosophy." In his Preface the author says; "As the NOËTICA imply all those instructions and means, that relate to the conduct of the understanding in pursuit of the knowledge of truth; so the ETHICA imply all those instructions and means, that relate to the regulation and conduct of our affections, actions, and behaviour in pursuit of the enjoyment of our true and chief good." Both these works were printed by Franklin and Hall, in Philadelphia. — EDITOR.

K*

greatest improvement will thereby be made in the most useful parts of physics. I conceive that fermentations of all sorts arise from electricity, and that the life and vegetation of animals and vegetables arise from fermentation. If so, the knowledge of electricity must give great light in medicine and agriculture. For this reason, I will gladly take pains to remove any difficulties you may have in receiving or conceiving these principles. I have not, as yet, heard that the tract on the "Principles of Action in Matter" is published, though I had the first sheet sent me in January last.

I am, &c.

CADWALLADER COLDEN.

P. S. This having lain by me some days for an opportunity to send it, I have, in that time, seen in the newspapers the account of the electrical kite.* I hope a more perfect and particular account of it will be published, in a manner to preserve it better, and to give it more credit, than it can obtain from a common newspaper. I wish you would attempt some experiments to ascertain whether the electrical fluid can be drawn from fermentary liquors or mixtures. I propose to try; but what may fail with me may succeed with you, as you have such sagacity in contriving proper experiments for any purpose you may have in view. The clouds, before a thunder-gust, and often in the time of it, appear to be in a violent intestine motion or fermentation.

Alluding to Franklin's celebrated experiment with a kite, to bring lightning from the clouds. See an account of this experiment in Vol. V. p. 175.- EDITOR.

Physical and Meteorological Observations, Conjectures, and Suppositions.*

READ AT THE ROYAL SOCIETY, June 3d, 1756.

THE particles of air are kept at a distance from each other by their mutual repulsion.

Every three particles, mutually and equally repelling each other, must form an equilateral triangle.

All the particles of air gravitate towards the earth, which gravitation compresses them, and shortens the sides of the triangles; otherwise their mutual repellency would force them to greater distances from each other.

Whatever particles of other matter (not endued with that repellency) are supported in air, must adhere to the particles of air, and be supported by them; for in the vacancies there is nothing they can rest on.

Air and water mutually attract each other. Hence water will dissolve in air, as salt in water.

The specific gravity of matter is not altered by dividing the matter, though the superficies be increased. Sixteen leaden bullets, of an ounce each, weigh as much in water as one of a pound, whose superficies is less. Therefore, the supporting of salt in water is not owing to its superficies being increased.

A lump of salt, though laid at rest at the bottom of a vessel of water, will dissolve therein, and its parts move every way, till equally diffused in the water; therefore there is a mutual attraction between water and salt. Every particle of water assumes as many of salt as can adhere to it; when more is added, it precipitates, and will not remain suspended.

* The date of this paper is uncertain. Its various parts were probably written at different times. It was sent to Mr. Collinson, with other philosophical papers, and a letter dated November 23d, 1753. See Vol. V. p. 314.- EDITOR.