EDITORIALS. 637 



This information can only be obtained in practical form for each 

 district, as the work of the Survey advances. Professor Shaler 

 has prepared a paper on the subject of geological highways, 

 which will be printed in the annual report of the Director of the 

 Survey for 1893-4. For more detailed information, it is proposed 

 that the various road commissioners send to the Survey samples 

 of such rocks and gravels in their immediate vicinities as are 

 believed to be valuable for road construction. 



A laboratory for inquiry into the value and use of mate- 

 rials which may be useful in the construction of highways was 

 established in connection with the Massachusetts Road Commis- 

 sion at the scientific department of Harvard University. This 

 was established especially to meet the needs of Massachusetts. 

 The results of the first year's work have shown clearly that the 

 laboratory will be of great service to the people. It is possible 

 that each state should establish a laboratory, though this would 

 lead to great expense, since the amount of work to be done after 

 a year or two of study would be relatively small in each, and the 

 results obtained by divers observers and methods would lack the 

 unity which give a national value. 



The work of the laboratory should be arranged so as to 

 obtain information ( 1 ) as to the resistance of the material to 

 blows such as are inflicted by the feet of draft animals and by 

 carriage wheels; (2) as to the cementation value of the dust 

 which is made when the bits of stone are placed upon the road 

 and driven together by the weight of the roller; (3) as to the 

 extent to which the stone is likely to be penetrated by water, 

 which, on freezing, will break and disturb the road-bed. When 

 preliminary tests have shown that any given material is likely to 

 be valuable, it may be desirable to make further and more thor- 

 ough tests by paving a square rod of some street where the 

 amount of traffic is sufficient to give it a thorough trial. 



Experience has shown that many kinds of rock which are 

 not suitable for road building when used alone, maybe combined 

 with other materials in such wise as to give good results. Thus 

 certain quartzites, which, though very hard, do not, when crushed, 



