He was elected to this chair and at about the same time was also chosen curator of the Illinois State Natural History Society, whose collections were domiciled in the museum of the Normal University.
Attracted by the Far West as a field for profitable scientific research, the summer of 1867 found him using his salary and the other available funds to defray the expense of an expedition to the then Territory of Colorado for the purpose of securing collections.

He organised and outfitted at Plattsmouth, Nebraska.

All his assistants were volunteers except the cook.

A.H.Thompson, afterwards so closely associated with him in the detailed exploration of the Colorado and in subsequent survey work, was the entomologist of the party.

They crossed the plains with mule teams to Denver, worked along the east slope of the Front Range, climbed Pike's Peak, and went westerly as far as South Park.