I have received your kind Favour of 19 Jan: and immediately communicated its Contents to Mr. Bowdoin, who desires me to give his most affectionate Regards to you and to tell you that he hopes he shall have an Opportunity of presenting to the Accademy here, the Papers you refer to.

The Discovery of freshening salt Water is no longer a Secret and I inclose a Description of the Machine with what I suppose to be the Principles of the Operation. This so much admired Discovery when a Mystery, is now laughed at by most People, because it is so simple. For my own Part I confess myself highly gratify’d and though I very much Doubt the Use of the Discovery, as first imagined (at Sea), I think it may be applied to a great Variety of usefull Purposes. In many Instances we depend on the precipitation of the Particles to clarify Liquids, and in many Instances the specific Gravity of these Particles is so small that they descend very slowly. Now in this ascending Filtration liquid Particles being extreemly divisible, and globular will easily find Passage; while everything else is catched by the Way, and their Gravity at some Time is constantly increasing by adhering one to another, as they more willingly stay behind.

This machine is supposed to have failed because it is supposed the Land will require often changes so it would be necesaary to carry in Water. I will not hesitate to tell you an Idea that strikes one on the subject, because I know you are not displeased at seeing a Disposition for Observation and Conjecture which though in the first Instance may be useless may be a step towards something else. I remember seeing some Experiments by Mr. Charles on the incompressibility of Water, and it appeared that it would find its Way through the Pores of the closest Metal rather than be compressed. When I heard that this Mr. Allen took a Water spout for his Principle, I conjectured that his Art consisted in producing an Artificial Evaporation, and Charles Experiment came immediately to my mind. If I had had a proper machine I should have tried to compress Salt Water, and if what escaped had been fresh I should have thought my Idea a good one. I did not choose to mention this before making the Experiment. because I suppose most of the Errors in Physics arise from too hasty conclusion without that Authority. Now that this Secret is known I feel a Confidence in my Conjecture and I mean to try thus. Place over a Tub a large Stone of a greater Diameter than the Tub, and so close as to leave no Passage for the Water between it and the Edge of the Tub, then connect the Tube F with the inside of the Tub, and if the Column is heavy enough to force the Water through the Pores of the Stone, it seems probable that the medium will not be so liable to become Salt as the Sand is. If this should not succeed I mean to try some other medium, and perhaps at last one may be found to answer, if so the Purpose originaly proposed will be effected. I mention this to you because I think you will imagine some Improvement of the Idea and kindly instruct me. You will please to remember that the drawing I inclose is only what I suppose from verball Discription the machine is, having never seen it, So what may appear to you defective should rather be imputed to my Error, than that of the Inventor.

You once desired me to give you in writing an Account of my recovering my Babe after apparently dying. I was desired by Dr. Larthrop to give it to him in order to give a Spur to the Establishment of a Society here; I accordingly wrote him the inclosed Letter and made one Budget of all I ha to say on the Subject. You will find yourself quoted in   and you will probaly find also that my Ideas are borrowed from you, this, as I told you before, you will always find for if I should ever have any pretention to Merit, it will be that of having attended to your frequent and instructive Conversing. I shall be glad if you will return the Paper to me when I see you again at Philadelphia as I have no other Copy of it.

Remember me affectionately to Mr. and Mrs. Bache Billy Ben and all the Family. Aunt Mecom and all our Family are well, she dined with us yesterday. I rejoice to find you in another Year, in Health, and cheerfullness. I pray God it may continue for many more. I am as ever most dutifully and affectionately Yours