THE UNITED STATES GEOLOGICAL SUE VET. 491 



tematic manner possible. The work is essentially economic, and, 

 owing to its intimate relations to geology, is considered to be 

 directly germane to the work of the survey. 



Highivays. The geology of highways embraces the study of 

 the materials entering into their construction. It is distinct from 

 the engineering problem of the mechanical construction of high- 

 ways a subject that is not intended to be taken up by the sur- 

 vey. The main questions have to do with the choice and manip- 

 ulation of materials. Experience has shown that many kinds of 

 rocks, which are not suitable for road-building when used alone, 

 may be combined with other materials in such wise as to give 

 good results. It is well known that in many districts great ex- 

 pense has been incurred in building roads on the best known 

 engineering principles of road construction, with the result of 

 producing dusty roads in summer and muddy roads in winter. 

 This outcome is the result of ignorance in regard to the character 

 of the rock necessary for the production of good roads. Inferior 

 materials have sometimes been used when there were other ma- 

 terials in the immediate vicinity which alone or in combination 

 would have produced a solid roadbed. A large part of the coun- 

 try, including the greater portion of the southern States and some 

 portions of the Mississippi basin, has been thought to be essen- 

 tially destitute of materials suitable for the construction of good 

 roads. The inquiries that have been made by geologists have 

 shown that in many places within these regions there are hidden 

 deposits of gravel and other sorts of rocks which, when properly 

 used, might give excellent highways ; and that around the mar- 

 gin of this great area, often within the limits of convenient rail- 

 way distribution, there are abundant supplies of rock well fitted 

 for such use. It only remains to discover the supply of such 

 rocks as are cheapest and best for each region. This information 

 can be obtained in practical form for each district as the work of 

 the survey advances. 



The movement for the betterment of roads and the obtain- 

 ment of information relating to the materials available for the 

 purpose has not yet taken a national character; but it is believed 

 . that, by establishing a laboratory in connection with the Federal 

 survey, a great impulse may be given to the improvement of 

 highways. Such a laboratory should be arranged to obtain in- 

 formation as to the character of the material best adapted to 

 road construction, tests being made of specimens sent to the 

 survey by the various road commissioners immediately inter- 

 ested, by geologists surveying areal geology, and by public- 

 spirited citizens interested in the making of good roads. During 

 the present year the survey is temporarily using a laboratory, 

 under the direction of Prof. N. S. Shaler, at the Harvard Sci- 



