entific School, Cambridge, Mass. Attention has been called to the use of bricks for highways, such as have been used for centuries in Holland and the lowlands of Europe. It now seems not only likely that this kind of pavement may become of great value in the south and the lower Mississippi Valley, but also important that the investigation of the clays of the country, with reference both to distribution and burning qualities, should be undertaken. Much information is at hand concerning the clays of many portions of the country, but little attention has been paid to their availability for making paving bricks.
Limitations of Economic Work. There have been and will continue to be differences of opinion as to the line to be drawn in economic work between that belonging to the States and individuals and that coming fairly within the field of the Federal survey. Broad interstate problems are clearly of the latter class, also those that by full study and elucidation will aid development in other areas. A test of the value of a high order of areal and economic work is brought out by a comparison of old and new conditions in the Rocky Mountain region. When the country was new, prospectors made many discoveries, and often accumulated fortunes with pick, shovel, and pan. These conditions have begun to pass away; and the mining industry now demands the highest skill and every assistance that can be given to it by geology and its collateral branches. The mining expert who is equipped with a full knowledge of the geology of the district in which he is working will succeed where the untrained man would fail. The new conditions will dominate even more in the future, rendering necessary a full knowledge of the geologic conditions surrounding mining problems. The work of the survey is not that of the prospector, nor that of the mining engineer who develops the property—that is the work of the individual, company, or community. The Geological Survey will give them the maps and the geologic data, and, if it will, the State can also aid by having analyses made for the prospectors, as well as detailed examinations and reports of special properties and of special methods of mining, treatment of ores, types of mining machinery, etc. Cases will arise when the study of a general problem will require the geologist of the Federal survey to make minute and detailed study of a mining district; but, as a whole, the work of the Federal survey is preparatory to the more detailed economic work of the State survey. The former will deal with broad interstate problems, and, when the States request it, co-operate in making a topographic map, and in the working out of such geologic problems as are germane to the work of the Federal survey.
Theoretic Work.—One of the criticisms often made of Government scientific work is that it is too theoretic in character and
