In the summer of 1860 he became principal of the public schools of Hennepin, Illinois.

These he organised, graded, and taught with a vigour which was characteristic, yet never forgetting his geological investigations in the neighbouring country, where, on Saturdays and at other times when the schools were not in session, he made botanical and zoological collections.
Convinced that war was inevitable, the winter of 1860-61 found him studying military tactics and engineering.

When the call came for troops, he was the first man to enroll, and largely through his efforts Company H of the 20th Regiment, Illinois Infantry, was raised in Putnam County.

When the regiment was organised at Joliet, Illinois, he was appointed sergeant-major, and in this capacity went to the front.
When the force was sent to Cape Girardeau, Missouri, his prescience in studying military engineering made him invaluable.

He was practically given charge of planning and laying out and constructing the fortifications at that place, a work he executed so well that it received the unqualified commendation of General Fremont.