Museum June 21st. 1808.
I am pleased that I can announce to you what I esteem an important improvement of the machinery of the Polygraph. Thinking on the subject the other day a thought occured that if the arm that connects the two pen-arms had a length nearly equal to the length of the Pen nib from the center of motion it would equalize the moovment. In short the longer the arm that joints with the connecting bar, provided it will conveniently shut up within the box, the better, for it is not in the least in the way in writing with either of the Pens.
A small Polygraph which I now write with only allowed me to lengthen said arm ⅝ of an Inch, which has added great value to the Machine. [GRAPHIC IN MANUSCRIPT] If the mooving the Joint from a to b has made an important improvement, than certainly to make it equal to whole distance of the point of the pen from the center of motion, would be still better. What I have said is more than sufficient for your comprehension of the subject. And I shall only add that I shall be happy to improve your Polygraphs in any manner you may please to direct. I made a small Polygraph for a Mr. Gilpin of this City with your improvment of the Cover falling [GRAPHIC IN MANUSCRIPT]and he has made a clever addition: Puting a board over the machinery with groves to fit the machinery, when foulded up, and in the vacant places let down Ink pots, boxes to hold Pens &c and the other part of the board is covered with green cloth. This when the Cover is laid down gives the Polygraph the appearance of a neat writing desk, & completly covers the Machinery from dust—and it has also the advantage of keeping the Machinery steady in travelling from place to place. Mr. Gilpin put a piece of paper over the Machinry which was folded up and the Gallows down, and marked the paper with black lead, this Paper placed on a board gave the place to be cut to fit the Machinry, some parts of which left very little substance in the upper surface of the board, but the cloth being glued on makes it sufficiently strong for the use of a careful Person.
Enclosed is a Publication which Mr. Hawkins sent me by the Ship Jane. He considers himself as he expresses it, an exile from his Country. I should like to posses one of his Claviole’s, and shall when I have rested awhile to recruit, for the great expences of late additions to the Museum and the aid given to my Son Rembrandt, desire Mr. Hawkins to send me one. I am now puting into practice some of the lessons which Rembrandt gave me on colouring, and my last Portrait is superior to any that I had painted heretofore. If I am allowed to continue my labours a few years longer, I may do some credit to the American Arts.
I am with much esteem your friend
DLC: Papers of Thomas Jefferson.