In 1857 Mr. Hitchcock was appointed assistant geologist to the Geological Survey of Vermont. He served the full term of the survey, and had charge of the preparation of the report relating to the stratigraphical geology, the measurement and delineation of the sections, and the compilation of the geological map. In 1861 he received the appointment of State Geologist of Maine, in which service he spent two summers in field work, preparing two reports of progress, which were published in connection with the report of the secretary of the Board of Agriculture. Besides the general reconnoissance, he discovered the existence of large areas of Upper Silurian and Devonian terranes. He has embodied his views of the distribution of the formations in his general map of the United States. Having chosen the ministry for his profession, Mr. Hitchcock studied theology under Dr. E. A. Park, of Andover, and the Rev. Dr. Taylor, of New Haven. Questions of the relations of theology and science were attracting much attention, and he treated of them in two papers in the _Bibliotheca Sacra_, one of which was afterward used for the guidance of theological students in several seminaries. As more opportunities were offered for scientific work, the ministry was given up. This was the time when the doctrine of natural selection came to the front for investigation, and the early history of mankind was receiving increased attention. Mr. Hitchcock came home from Europe in 1867 convinced of the truth of some form of evolution, of a considerable antiquity of man, and of the probability of a plural origin of the human race. Finding that some of his views on these subjects were not acceptable to his associates, he ceased to make them prominent in his class instructions, and devoted his attention to the more technical details of geology. Since then general opinion has advanced so far on these subjects that the views he held at that time seem now really conservative.