I recieved two days ago your letter of the 20th. and readily consent to pay mr Evans the usual compensation for his inventions employed in my mill, whenever you or he will be so good as to ascertain the amount. what these are I know not, having left to the millwright to do whatever he thought would be useful. she began to run in the autumn or winter of 1806. I make this paiment willingly as a voluntary tribute to a person whose talents are constantly employed in endeavors to be useful to mankind, and not as a legal obligation. my mill was erected after the expiration of mr Evans’s first patent & before the date of his second; and were there any doubt as to the proviso in the act covering those who adopted those machines when no law forbid it, the text of the constitution which declares that Congress should have no power to pass an ex post facto law, would annul any enactment of retrospective effect were there any such in the law in question. meaning however to claim nothing more than the justice of being considered as doing voluntarily what the law has not required, I shall recieve with pleasure a specification of the amount and tender you my respects.