“A gentleman presented specimens to the Troy Lyceum, from Illinois, of gypsum and secondary sandstone, and informed me that the latter overlaid the former in regular structure.  Myron Holly, and others, have given me similar specimens, which they represent as being similarly situated, from several localities in the western part of this State.  This secondary sandstone is sometimes more or less calcareous.  I believe it is used for a cement by the Canal Company, which hardens under water.  Will you do me the favor to settle this question?

“On your way to Detroit, you may perhaps, without material inconvenience, collect facts of importance to me, in relation to secondary and alluvial formations.  Anything transmitted to me by the middle of April on these subjects will be in season, because I shall not have printed all the transition part before that time.

“Have you any knowledge of the strata constituting Rocky Mountains?  Is it primitive, or is it graywacke like Catskill Mountains?  I have said, in a note, that, after you and Dr. E. James set foot upon it, we shall no longer be ignorant of it.

“I intend to kindle a blaze of geological zeal before you return.  I have adapted the style of my index to the capacities of ladies, plough-joggers, and mechanics.”

March 28th.—­While here, I received a notice of my election as a member of the Academy of Natural Sciences at Philadelphia.

April 28th.—­James T. Johnston, Esq., of N.Y., writes on the interesting character of the mineralogy of the interior of Georgia.

The spirit of inquiry denoted by these letters gives but a faint idea of the interest which was now awakened in the public mind, on the exploration of the west, and it would require a reference to the public prints of the day to denote this.  If the delay had served no other purpose, it had brought us into a familiar acquaintance with our commander, who was frank and straightforward in his manners, and fully disposed, not only to say, but to do everything to facilitate the object.  He put no veto on any request of this kind, holding the smiths and mechanics of the government amenable to comply with any order.  He was not a man, indeed, who dealt in hems and haws—­did not require to sleep upon a simple question—­and is not a person whose course is to be stopped, as many little big men are, by two straws crossed.

At length the canoes, which were our principal cause of delay, arrived from Lake Huron, where they were constructed, and all things were ready for our embarkation.  It was the 24th of May when we set out.  A small detachment of infantry had been ordered to form a part of the expedition, under Lieutenant Aeneas Mackay.  Eight or ten Chippewa and Ottowa Indians were taken in a separate canoe, as hunters, and gave picturesqueness to the brigade by their costume.  There were ten Canadian voyagers of the north-west stamp.  Professor Douglass and myself were the only persons to whom separate classes of scientific duties were assigned.  A secretary and some assistants made the governor’s mess consist of nine persons.  Altogether, we numbered, including guides and interpreters, about forty persons; a truly formidable number of mouths to feed in the “waste howling wilderness.”