492 THE POPULAR SCIENCE MONTHLY. 



entific Scliool, Cambridge, Mass. Attention lias been called to 

 the use of bricks for highways, such as have been used for cen- 

 turies 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 por- 

 tions 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 indi- 

 viduals 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 develop- 

 ment 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 coun- 

 try was new, prospectors made many discoveries, and often ac- 

 cumulated 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 de- 

 velops 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 ex- 

 aminations and reports of special properties and of special meth- 

 ods 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 geo- 

 logic problems as are germane to the work of the Federal survey. 



Theoretic Work. One of the criticisms often made of Gov- 

 ernment scientific work is that it is too theoretic in character and 



