Geological Survey of Dutchess County.—­Dr. Benjamin Allen, of Hyde Park, writes to me (June 4th) on this subject, urging me to undertake the survey; but the necessity of closing my engagements in the West rendered it impossible.

Expedition of 1820.—­Dr. Mitchell furnishes me opinions upon some of the scientific objects collected by me and my associates in the north-west in 1820:—­

“The Squirrel sent by General Cass is a species not heretofore described, and has been named by Dr. Mitchell the federation squirrel, or sciurus tredecem striatus.

“The Pouched Rat, or mus bursarius, has been seen but once in Europe.  This was a specimen sent to the British Museum from Canada, and described by Dr. Shaw.  But its existence is rather questioned by Charles Cuvier.

“Both animals have been described and the descriptions published in the 21st Vol. of the Medical Repository of New York, p. 248 et seq.  The specimens are both preserved in my museum.  Drawings have been executed by the distinguished artist Milbert, and forwarded by him at my request to the administrators of the King’s Museum, at Paris, of which he is a corresponding member.  My descriptions accompany them.  The originals are retained as too valuable to be sent out of the country.

“The Paddle Fish is the spatularia of Shaw and polyodon of Lacepede.  It lives in the Mississippi only, and the skeleton, though incomplete, is better than any other person here possesses.  It is carefully preserved in my collection.

“The Serpent is a species of the Linnaean genus Anguis, the orveto of the French, and the blind worm of the English.  The loss of the tail of this fragile creature may render an opinion a little dubious, but it is supposed to be an ophias aureus of Dandin, corresponding to the Anguis ventralis of Linn, figured by Catesby.

“The shells afford a rich amount of undescribed species.  The whole of the univalves and bivalves received from Messrs. Schoolcraft and Douglass, have been assembled, and examined with all I possessed before, and with Mr. Stacy Collins’s molluscas brought from Ohio.  Mr. Barnes is charged with describing and delineating all the species not contained in Mr. Say’s memoir on these productions of the land and fresh waters of North America.  The finished work will be laid before the Lyceum, and finally be printed in Silliman’s New Haven Journal.  The species with which zoology will be enriched will amount probably to nine or ten.  We shall endeavor to be just to our friends and benefactors.

“The pipe adorns my mantelpiece, and is much admired by connoisseurs.”

CHAPTER VII.

Trip through the Miami of the lakes, and the Wabash Valley—­Cross the grand prairie of Illinois—­Revisit the mines—­Ascend the Illinois—­Fever—­Return through the great lakes—­Notice of the “Trio”—­Letter from Professor Silliman—­Prospect of an appointment under government—­Loss of the “Walk-in-the-Water”—­Geology of Detroit—­Murder of Dr. Madison by a Winnebago Indian.