Mr. Du Bois entered the Mint in September, 1833, and was first employed in the office of the Director, Dr. Moore. In 1835, at the request of the Assayer, Mr. Jacob R. Eckfeldt, he was transferred to a more congenial position in the assay department. Here he continued for the remainder of his life. In 1836 he was appointed Assistant Assayer. In September, 1872, he succeeded Mr. Eckfeldt as Assayer, and remained at the head of the department until his death, July 14, 1881, thus completing nearly forty-eight years of Mint service. Mr. Du Bois early took rank as an accomplished assayer, and long before his death had reached the head of his profession. The close intimacy between Mr. Du Bois and Mr. Eckfeldt developed into warm friendship. The tie was made closer by the marriage of Mr. Du Bois, in 1840, to Susanna Eckfeldt, the sister of his chief. I shall have to speak of published works and scientific communications appearing under the names of Eckfeldt and Du Bois. Although it was understood that Mr. Du Bois was the sole literary author, yet no separate claim of authorship was made by either. Whatever of reputation was earned, each was contented that it might be shared by the other, and jealousy never for a moment weakened a union that bound them for life. In the year 1834 a change took place in the ratio of gold to silver in the standard of U. S. coins, the effect of which was to bring large deposits of gold to the Mint. The coinage previously had been chiefly of silver. The more equal supply of the precious metals gave active employment in the assay of each of them, and was, of course, most valuable as an experience to Mr. Du Bois, who about this time became connected with the assay department. In 1837, on revision of the Mint laws and standards brought about by Dr. Robert M. Patterson, then Director, a reform was effected in the method of reporting assays, the millesimal system taking the place of the time-honored but cumbrous method of carats and grains. About this time, also, the older plan of assaying silver was abandoned, the humid assay being substituted, and largely worked under the direct supervision of Mr. Du Bois. About 1838 branch mints were organized in the States of Louisiana, Georgia, and North Carolina. The labors and responsibilities of the Philadelphia assay department were increased by this development, partly from the necessity of instructing assayers for the new branches, and partly in testing the correctness of the assays made there.