Your favor of the 23d. is recieved. I think the improvement by your son, of lengthening the pen-bar to the left is an excellent one. by lessening the breadth of the rhomboids or parallels, it lessens the projection of their corners when folded up, and of course permits a shortening of the polygraph from East to West. I think it will enable you to reduce that dimension to 16. I. in the clear (being the double breadth of letter paper) and 10. I. from North to South in the clear. and such a reduction is really important even for those not meant to be carried about. the one I am writing with, tho’ a most excellent one, is inconvenient from it’s occupying so great a space on a table, to wit 22. by 32. I. when by the new improvement 17½ by 24½ would do, which is but ⅔ of the area. I think you will find on trial that 2. vertical rhomboids of 5. I. each, will command the whole page in my model, and shut up within the space. [GRAPHIC IN MANUSCRIPT] because the gallows a.b. being 8. I. in the clear, and the paper board a.c. the same, the line b.c. is but 8¾ I., and requires 2. rhomboids of 5. I. only, which will certainly shut up on the North board a.d. because 3. five inch rhomboids do that in the model. I think therefore that 5. I. rhomboids will command the whole of the South board, & shut up on the North one. but still this is theory; while you will be controuled by the law of practice. I have, since my return, thoroughly tried the desk polygraph you left here. it does not at all command the page. I do not wonder at Mr. Beckley’s returning it, & think it would not be for your interest to sell it till you have had it in your own hands. I will therefore have a box made for it, & will forward it to you by water with the box of minerals. the Polygraph for mr Volney must be reserved for some vessel bound to Havre, that it may get to Paris by water. Accept affectionate salutations.