Monticello Jan. 15. 21.
Th: Jefferson presents his thanks to mr Hayden for his Geological essays, which he has been so kind as to send him. he has indulged himself but little in that branch of science, deterred by the magnitude of the object, and shallowness of our means. yet the pursuit is worthy of encouragement as it may produce other utilities. he prays mr Hayden to accept his respectful salutations.
ViU: Papers of Thomas Jefferson.