Jefferson’s copy was sent to him by the author through David Baillie Warden, who wrote to Jefferson from Paris on June 12, 1808, to say that he had sent certain books, including “ Cossignys’s work on Powder &c.,” the authors of which were anxious to hear of their arrival.

This refers to the first part only which Jefferson had bound by Milligan, cost $0.50, listed on his bill under date April 30, 1808.

Joseph François Charpentier de Cossigny, 1730-1809, French naturalist, was capitaine-ingénieur du roi.

Jefferson’s copy was a presentation from the author, who wrote from Philadelphia, June 6, 1798: “To you as a philosopher, and a man of science I take the liberty of submitting the treatise which accompanies this letter; and, urged by a consideration that the subject is of consequence to the United States, I further presume to request that you will be good enough to favour me with such observations as may occur to you on the perusal of it, tending to designate error or facilitate improvement.”

Jefferson replied from Philadelphia on June 12: “ Th: Jefferson returns his thanks to m( ^~ r) Fennel for the Dissertation on his method of making salt. the theory is certainly promising. what may be the actual result depends on so many circumstances as to require experiment to found an estimate. having no experience on the subject himself, he is entirely unable to give an opinion; but doubts not that m ( ^~ r) Fennel has sufficiently verified his process by experiment to justify his conclusions. he sincerely wishes him success, and apprehends the circumstances of the times are likely to befriend his undertaking. ”

James Fennell, 1766-1816, English actor and dramatist, came to America in 1793 at the invitation of the manager of the Philadelphia Theatre, and settled in the United States. This book, dedicated to John Adams, the President, explains his plan to extract the salt from sea water, and in 1814 he established salt works near New London, Connecticut. All his salt plans resulted in financial loss.