I have duly received your letter on the subject of Mr. O. Evan’s application for a patent. As the application is founded on a decision of the Circuit Court at Philadelphia, against the validity of a former patent for the same invention, a compliance with it would admit the invali⟨dity⟩ of all the patents issued in the same form since the commencement of the government. Such a principle I did not think myself justified in introducing on that authority alone. I am &c.