Philada 14 Nov 1806
I recd your favour by this Days post and should immedeately have put your spects in hands but I concieve you are in a mistake as to the distance of the centre of the eyes you mention 2½ inch from centre to centre. I do not find the largest of my spectacles so wide wishing to making them to please and recolecting the President has but a small head I wish them examined again, it will be observed when a person is looking at a book or any object say about 15 inches distance both eyes meet at a point, consequently the spectacles being about 1¼ Distance from the eye the centre of the spects should be rather nearer than the eyes. submitting to your direction please to write me by return of post. I have done a number of spects with near & distant focus in each eye, I fitted 2 pair lately for Mess Jas & Charles Peale for painting miniatures that answer extremely well. it would assist me much if the President could give me the focal distance of the spectacles daily used which is easily done by the distance the image is formed in a door or wall that is white in a long entry opposite to where the sun is reflecting: by knowing this I may suite you easier with 2 or 3 pair of glasses than otherwise by a great many I shall with pleasure wait your orders.
I am sir yours respectfully
PS If a glass could be taken out of an old spets that suites your sight and enclosed in a letter it would assist me greatly
DLC: Papers of Thomas Jefferson.