GEOLOGY IN SERVICE OF MAN WATTS 277 



successors when Ave have picked out the best. This has ah-eady 

 been to some extent effected for oil and it is beginning for coal ; 

 it must eventually be done for the still less pure sources of these two 

 substances, for less concentrated ores, and the like. 



Sto7ie, etc. — The geologist has alread}^ done much in the investiga- 

 tion of the qualities of building stones, plastic substances, and the 

 materials for roofing and cement. To a large extent the materials 

 in use are satisfactory in the air and surroundings in which they 

 occur in nature. But the added problems of a town atmosphere, 

 accompanied by increased stresses in large buildings and the modern 

 demands of the architect and sculptor, have still to be met, if our 

 buildings are to be more permanent and our towns to present a loss 

 weather-beaten aspect than they noAv do. New and reliable means 

 of testing are required, and we need a more thorough understanding 

 of the reactions produced by impure atmospheres and the effects 

 of the presence or absence of protective or destructive organisms. 

 Future investigation will react in the production of more satisfac- 

 tory preservatives, and it ma}'^ lead to increased production and 

 adoption of artificial stones devoid of the qualities which undermine 

 the power of resistance of natural stones; at the same time more con- 

 trol over color and shaping may be obtained. 



Roads. — Closeh" akin to the subject of building materials comes 

 that of stones used for flagging, paving, and metalling of roads, to 

 the provision and stud}^ of which the geologist has already very 

 largely contributed. New problems are daily introduced as road 

 traffic becomes heavier and as roads are required to be freer from 

 dust and vibration. Already many waste products have come into 

 valuable utilization, and a wide range of road metals which can be 

 called upon for these purposes exists in almost every country. 



In the siting of roads, railways, and canals, however, geology 

 could render much more useful service than it has yoX been called 

 upon to give. The routes that are cheapest to make are by no means 

 the cheapest to maintain, and the geological survey of routes Avould 

 very often suggest slight deviations which Avould be more econom- 

 ical in the end than when the shortest route compatible with the 

 gradients is taken. 



The princes of road makers in the old world, the Komans, were 

 perhaps too heroic in their dealings Avith gradients, but they exer- 

 cised quite remarkable skill in choosing such directions as to secure 

 the least formidable slopes consistent Avith the general design of 

 their routes. Their roads Avere, however, constructed ju-imarily for 

 strategic purposes and secondarily for transport, and it Avas neces- 

 sary to sacrifice something. On the other hand, the constructors of 

 76041—26 19 



