And there, in Washington, the year through, Roger found expert and skilled men making these maps, compiling them from the sketches made in the field, correcting minor errors, comparing them with former data, and producing works of exactitude and immense value. Some idea of the exactness of the work was gained by the boy when it was pointed out to him that in the Bureau of Engraving the printing of all this exact drawing must be done in a room where the temperature and humidity are the same the year round, since paper will shrink in a dry spell and expand when moist, and the printing of such a map extending over a period of months, might thus be made fractionally incorrect. Then it dawned upon the lad that the libraries of scientific records of which Survey workers are the authors must needs require time and labor, and the compilation of statistics needed in other parts of the government service also takes up time. So that Roger began to see that the proofreading of all geologic and topographic maps, all illustrations and all text of Survey papers have to be done and revised by competent men, in order that the scientific accuracy of these can never be impeached. He saw the scope of the annual reports, the monographs, the professional papers and the bulletins, and was not surprised to learn that these were in great demand, not only in the United States, but by foreign governments as well. "But all this," said Roger to his friend the secretary, as they were talking together one day, "must cost the country a heap of money." The other smiled. "It has saved the country a great deal of money," he said. "In the first place the Survey is very economically run, and then besides, millions of dollars have been put into the hands of manufacturing interests by pointing out to them the value of by-products which formerly were wasted." "For example, Mr. Mitchon?" "Well, for example, the waste of the by-products of coke-ovens, such as coal-tar, ammonia, etc.," replied the secretary. "Here, come with me to the laboratories, and I'll show you." In the large chemical and physical laboratories at Washington the boy found samples of metals and minerals of all sorts being tested and analyzed. He found that all the great works of the government are undertaken only with the advice of the Geological Survey, and he learned, moreover, that in certain branches the Chemical Laboratories stand higher than those of any government in the world.