Th: Jefferson presents his compliments to mr Porter and his thanks for the specimen of Gypsum he has been so good as to send him—he recollects that when mr Ellicot returned from some survey on lake Erie, he brought specimens of exactly the same appearance found on or near that lake. it is to be hoped then that the vein has some extent. he wishes the inland navigation thro’ which it must pass from Camillus to N. York may be able to deliver it there at a more reasonable price than it has been at for two years past. (14.D. at Baltimore) which has nearly suspended it’s use. he salutes mr Porter with respect.