1Thomas Jefferson to Peter B. Porter, 8 March 1811 (Jefferson Papers)
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...