Your favor of the 12th. is duly recieved, and I have no doubt the idea you suggest is perfectly sound that the glasses of spectacles should perfectly accord with one another. the surfaces of every lens for a spectacle should be a portion of that of a sphere, and not only should the two convexities correspond in position, but also with the lines of vision from the two eyes. my improvements in spectacles have been trifling, being confined merely to size & form. I have adopted Dr. Franklin’s plan of half glasses of different focal distances, with great advantage.   —I shall leave this place within a week for Monticello. Capt. Lewis will set out about the same time for Philadelphia. by him I will send the small reimbursement of 2. D 05 c for the inkholders. Accept affectionate salutations.