He requests me to furnish him a copy of my memoir on the geology of the regions visited by the recent expedition, or, if it be too long for the purposes of the _American Journal_, an abstract of it.
_Animal Impressions in Limestone_.--"I am much obliged to you for your kind intention of furnishing me with a paper on the impressions in limestone, and I hope you will bear it in mind, and execute it accordingly.
"I have observed the appointment which the newspapers state that you have received from the government, and regret that it carries you so far south,[11] into an unhealthy climate; wishing you, however, health and leisure to pursue those studies which you have hitherto prosecuted so successfully." [Footnote 11: This is evidently an allusion to St.Mary's, in Georgia, instead of Michigan.] Professor Frederick Hall, of Middlebury College, addresses me (Jan.
14th) on the same subject.

He alludes to my treatise "On the Mines, Minerals, &c., of the western section of the United States;" a work for which our country and the world are deeply indebted to your enlightened enterprise and unrelaxing zeal.

Before reading it, I had a very inadequate conception of the actual extent and riches of the lead mines of the West.

It seems, according to your account, that these mines are an exhaustless source of wealth to the United States.

"I should feel glad to have them put under your superintendence; and to have you nurture up a race of expert mineralogists, and become a Werner among them." Professor Silliman writes (Jan.