In 1848 the great discovery of gold in California was made known. This brought a tremendous pressure on every department of the Mint, and not the least on the assayers. The gold coinage was, in three years, raised from a little over three million dollars to more than sixty-two millions. The assays were often counted by hundreds in a day. But whatever the pressure in the office, accuracy ruled, and the correctness of the assays was never impeached. In 1853 a change was effected in the law for providing subordinate silver coins. This brought about, for some years succeeding, an unprecedented coinage of that metal, and still further increased the labors of the assay department. He instituted the Cabinet of coins which now adorns the Mint. This was commenced in 1838. A small annual appropriation was procured from Congress for this purpose, and the work of collection committed entirely to Mr. Du Bois. He brought to it all the enthusiasm which animates most numismatists, sobered, however, by good judgment. His expenditures were always judicious. Some of the best of the specimens were culled from the Mint deposits for the bullion value, merely, of the pieces. After the collection had taken good shape, and been well classified, he wrote and published, in 1846, a description of it, under the title “Pledges of History,” etc. The title thus selected intimated his opinion as to the real value of such collections. He thought that a coin should be prized for its historical teaching, or artistic merit, and discouraged the rage to possess a piece simply because of its rarity. Mr. Du Bois acted as curator of the Cabinet until his death. Another important labor undertaken by Mr. Du Bois (in connection with Mr. Eckfeldt) was the preparation and publication, in 1842, of a “Manual of the Gold and Silver Coins of all nations, struck within the past century.” This was a work of very great labor, and, from its expense, of some risk also to the authors. It is admirably arranged, the information clear, and it embraced every subject of interest at that date as to coins, bullion, counterfeits, etc. Subsequently, in 1850 and 1851, supplements were published covering later topics, made prominent in consequence of the California gold discoveries.