FKKNCH TESTS. 17 



steadily developed ever since. The Portuguese ( lovernment . the next 

 to take up the subject. ado])ted some of (he French tots and conducted 

 them with much precision. While- the importance of the subject has 

 been recogni/ed in England, vet aside from the limited in\ est i^at ions 

 of a few individuals, almost nothing has been done. The same is 

 true, even to a greater extent, of Germany, and the other continental 

 nations have left the subject practically untouched. The United 

 States is the only other country where this work has been carried on 

 in a systematic way. 



In 1893 the Massachusetts highway commission, in collaboration 

 with the Lawrence Scientific School of Harvard University, estab- 

 lished a road-material laboratory at the latter institution. Although 

 paving-brick tests had been made previously, this was the first labora- 

 tory in the United States for testing road materials in a systematic 

 way. The Deval abrasion test was adopted, and tests for determining 

 the cementing power of rock dust were first developed there. Since 

 then laboratories have been equipped with appliances for testing road 

 materials by the Maryland Geological Surve} T , Columbia University, 

 Wisconsin Geological Survey, Cornell University, the University of 

 California, and the United States Department of Agriculture. 



TESTS OF ROAD MATERIALS IN FRANCE. 



In December, 1878, the French commission on national roads 

 decided to introduce certain mechanical tests at the laboratory of the 

 School of Roads and Bridges, to be conducted in addition to and par- 

 allel with service road tests. The Deval test, bearing the name of its 

 designer, for determining the resistance offered by macadam rocks to 

 abrasion had already been pronounced by the street department of the 

 city of Paris to be useful and reliable in testing the rock used in con- 

 tract work and for selecting new quarries. This test was accordingly 

 adopted by the commission and a laboratory was founded, which has 

 steadily increased in usefulness. 



THE DEVAL MACHINE. 



This machine, as far as the writer has been able to ascertain, was 

 the first one designed especially for testing road materials. It was ti r-t 

 exhibited at the Paris Exposition of 1878, and then con>isted of two 

 iron cylinders fastened to a shaft, so that the axis of each cylinder \va- 

 at an angle of 30 degrees with the axis of rotation. The shaft which 

 held the cylinders was supported on bearings, and had at one end a 

 pulley wheel by which the cylinders were revolved and at the other 

 a revolution counter. Each cylinder, 20 cm in diameter and 34 cm 



6090 No. 7903 2 



