384 



ANNUAL REPORTS OF DEPARTMENT OP AGRICULTURE. 



construction and maintenance. Beginning May 13 tlie Fuel Acluiin- 

 istration refused to issue permits for the use of such materials in 

 highway work unless applications were first made to the Director of 

 the Office of Public Roads and Eural Engineering and the work 

 approved as an urgent necessity. 



The work of the Conference of State Highway Testing Engineers 

 and Chemists, held during the fiscal year 1917, was supplemented by 

 the preparation of two bulletins, both of which have been published. 

 In general, the recommendations of the conference were followed, 

 with a view to standardizing specification requirements of all types 

 of road materials. 



Twelve hundred and ninety-eight samples were analyzed in the 

 laboratories during the fiscal year. The decrease of approximately 

 4 per cent as compared with the preceding year is considered very 

 slight in view of present conditions. 



ROUTINE CHEMICAL TESTING AND INSPECTION. 



Two hundred and eighty-nine samples were examined in the chem- 

 ical laboratory. This represents a total decrease of something over 

 3 per cent as compared w ith the preceding fiscal year. It is expected, 

 however, that a marked increase wilf be shown for 1919, owing to 

 check tests which will be made on samples of materials used on 

 Federal aid projects. Of the samples examined 255 were bitumi- 

 nous materials, 12 metal, and 22 sand, soil, and miscellaneous 

 materials. 



PHYSICAL TESTS OF ROAD BUILDING MATERIAL. 



The physical laboratory tested 1,009 samples, an increase of nearly 

 10 per cent, as compared with the preceding fiscal year and well 

 above the average amiual routine testing. Of these samples, 571 were 

 rock and slag, 117 gravel, 206 sand, clay, soil, etc., 90 cement and 

 concrete, 8 brick, 5 oil, and 12 miscellaneous. Samples were received 

 from all but 12 States of the Union. States from which the largest 

 number of samples were received are as follows: 



Maryland 200 



Virginia 154 



Massachusetts ] 14 



Pennsylvania 89 



New York 67 



Ohio 53 



North Carolina 50 



Connecticut 44 



New Jersey 43 



South Carolina 2G 



The results of ph^^sical tests of road-building rock in 1916 and 

 1917 were published as Department Bulletin 670. 



MICROSCOPIC EXAMINATION AND CLASSIFICATION OF ROAD-BUILDING ROCK. 



The microscopic laboratory examined and classified 630 samples 

 of road-building materials, a decrease of a little less than 7 per cent, 

 as compared with the preceding fiscal year, but well above the average 

 routine work. Of these samples, 322 were rock and slag, and 308 

 gravel, sand, clay, etc. 



Texas 24 



District of Columbia 22 



Alabama 20 



liOuisiana 15 



Vermont 14 



Arkansas 14 



Maine 11 



Missouri 10 



New Hampshire 10 



