I have duly recieved your letter dated May with the model of your mathematical instrument and it’s description. the addition of a graduated margin to the square drawing board and ⊢ parallel ruler in use is an ingenious thought, and capable of useful applications, particularly of those you suggest, and probably others which practice will discover. the wetting of the paper, to relieve it from it’s buckle, I found less troublesome than I had expected. what I most fear is the embarrasment of adjusting a 2d or 3d to the 1st paper when the lines happen to run out of the 1s[t]. you ask me to give an opinion which may recommend it to the public. this is an office I would not arrogate to myself in any line of science, much less in one wherein you have in your own city a judge so much more competent, Professor Patterson. age too has withdrawn me from abstruse speculations: and as to this instrument, I have considered it so far only as to understand it’s general application, but not to say what is the degree or number of utilities which may be derived from it. I return you the MS description because it may on some occasion save you the copying it: I will do the same, if you desire it, by the model. otherwise I am reluctant to embarras the mail with such packages. I salute you with respect and wishes that your invention may be as profitable to yourself as useful to others.

Th: Jefferson