His paleontological collections included a unique series of Trenton limestone fossils, which was sold in 1873 to Prof. Louis Agassiz, and his intercourse with Professor Agassiz at that time was most helpful and stimulating. An arrangement was made for Mr. Walcott to go to Cambridge and pursue a course of study under the advice and direction of the great naturalist, but this was frustrated by the death of Agassiz.
In November, 1876, he received his first official appointment, becoming assistant to Prof. James Hall, State Geologist of New York. While holding that position researches were made in New York, Ohio, Indiana, and Canada. In July, 1879, Mr. Walcott was appointed field assistant in the United States Geological Survey, then under the direction of Clarence King, and was assigned to the study of the great geological section extending from the high plateaus of southern Utah to the bottom of the Grand Canon of the Colorado. In 1882 he collaborated with Mr. Hague in the survey of the Eureka mining district of Nevada. The Palæozoic paleontology of the survey was now assigned to him, and, though this entailed considerable routine work in the identification of fossils brought from many fields by the various geologists, he was enabled to pursue with vigor his cherished plans for the investigation of the older faunas. He examined the Cambrian formations of the Appalachian belt all the way from Alabama to Quebec, and carried his researches on a more easterly line through New England and New Brunswick to Newfoundland. He also began a series of western studies which eventually included the most important known bodies of Cambrian rocks in Texas, Arizona, California, Idaho, Nevada, Montana, Wyoming, and South Dakota. In 1888 he was advanced to be paleontologist in charge of invertebrate paleontology in the Geological Survey; in 1891, to be chief paleontologist; and in 1893, to be geologist in charge of geology and paleontology, in which capacity he had charge of the general direction of that branch of the work of the survey. In July, 1894, Major J. W. Powell, after fourteen years' service as director of the survey, retired from that office, and Mr. Walcott was selected by President Cleveland to succeed him.
Mr. Walcott's service to science falls under two heads—research and administration. The scientific study which results in positive additions to the world's knowledge has a somewhat definite course, beginning with the observation of phenomena, proceeding with their arrangement in classes, and concluding with hypothesis and theory as to their natural sequence or genesis. Classification and hypothesis afford new points of view which lead to additional observations, so that the various steps of the process are to a certain extent alternated; but the most successful researches, those whose results