It was not, till yesterday that I received your kind Letter, with your Discourse on Animation; for both of which obliging favours I pray you to accept of my best Thanks.1

My incessant Drudgery for three and thirty Years in the dull fields and forests of Law and Politicks, has rendered it impossible for me to Spare much of my time, in disquisitions of natural Knowledge. Whenever any Thing of the kind however has accidentally fallen in my Way, it has revived the fond Attachment of my Youth, and given me more pleasure than I can account for.

There is no Physical Subject has occurred oftener to my Thoughts, or excited more of my Curiosity, than that which you chose for your Discourse, Animal Life. It has long appeared to me astonishing, that it should be impossible to discover, what it is, which the Air conveys into our Lungs and leaves behind it, in the Body when We breathe. This, whatever it is, Seems to be, the Cause of Life, or at least of the continuance and Support of it, in the larger Animals. whether the Air, in any Similar manner, Supports the Animalcules which We discover by Microscopes, in almost every kind of substance I know not.

Dr Franklin has sometimes described to me in Conversation, experiments which he made in various parts of his Life relative to this subject, which I hope will be found among his Papers. I should be afraid, upon mere memory of transient Conversation to repeat some facts which he related to me, of the revival of animalcules to perfect Life and Activity after ten Years of Torpor, in a Phyal which he left in Philadelphia when he went to England and which had not been handled till his return.

Pray where is the Evidence of the Existence of a Subtle Electric fluid which pervades the Universe? and if that fact were proved, where is your Authority for Saying that Such an Electrick fluid is the Cause of Life? Why may it not as well be Magnetism? or Steam, or Nitre? or fixed Air? These are all tremendous Forces in nature. But where and what is the Principle or Cause of Activity in all of them?

The Cause of Motion in all these Phænomena, as well as in the Emanations of Light, or the Revolutions of the Heavens or Gravitation on Earth, is Still to seek.

Your Discourse, my dear sir has given me great Pleasure, and, (if my Opinion is worth your having tho indeed I must acknowledge it is of very little value in Such Things) does honour to you, and to the Societies to which You belong.

With great Esteem, I am, dear sir / your most obedient & most / humble servant