To Dr. Samuel P. Hildreth we owe the first extended and connected account of the geology of the Ohio Valley. His published notes on the salt springs and interesting observations on the coal deposits, with descriptions of the rocks, fossils, organic remains, illustrated by drawings of plants and shells, constitutes one of the most comprehensive documents that has ever been made of the geology of the state. And it was through his influence the legislature took steps for a geological survey, which was ordered March 27, 1837, with a corps composed of doctors chiefly--Professor W. W. Mather, Dr. S. P. Hildreth, Dr. Jared P. Kirtland, Dr. John Locke, Dr. C. Briggs, Col. T. W. Foster, and Col. Charles Wittlesey. Dr. Kirtland was a model specimen of those noble men with great hearts, clear heads and diligent hands. He was no closet naturalist, but a student of nature in its full degree. In 1829, while studying the unios or fresh-water mussels, he discovered that authors and teachers of conchology had made nearly double the number of species which are warrantable. Names had been given to species in which was only a difference of form due to males and females of the same species. The fraternity of naturalists in the United States and Europe were astonished because of the value of the discovery and the _source whence it came_. There were hundreds and probably thousands of professors who had observed the unios and enjoyed the pleasure of inventing new names for the varieties. “A practicing physician in the backwoods of Ohio had shattered the entire nomenclature of the naiads.”[10] At the Cincinnati meeting of the American Association in 1852, Professor Kirtland produced specimens of unios of both sexes, from their conception through all stages to the perfect animal and its shell. Agassiz was present and sustained his views, and said they were likewise sustained by the most eminent naturalists of Europe.[11] And it is worthy of remembrance that it is only those who base their conclusions on observed nature that make permanent reputations, and show that theory and discussion do not settle any thing worthy a place in science.