OFFICE OF PUBLIC ROADS AND RURAL ENGINEERING. 371 



were 2,286 new slides colored for lecture work. Fifty-seven sets of 

 lantern slides were loaned to various individuals and organizations, 

 exclusive of those used in lecture work by employees of the office. 

 At the close of the year the photographic files contained 17,085 nega- 

 tives, 47,104 prints, 12,134 slides, and 1,328 bromide enlargements. 



ROAD MATERIAL TESTS AND RESEARCH. 



General lack of uniformity in specification requirements for all 

 types of road materials induced the office to call a conference of 

 State highway testing engineers and chemists for the purpose of 

 establishing standard forms of specifications and standard methods 

 of sampling, testing and reporting test results on road materials. 

 Twenty-one States sent representatives to Washington to attend the 

 conference, which was in session for six consecutive days. The recom- 

 mendations of this conference have been prepared for publication as 

 a department bulletin. These recommendations include 41 standard 

 forms of specifications for materials to be used in various types of 

 road construction. The materials covered are broken stone, stone 

 block, broken slag, gravel, sand, topsoil, sand clay, mineral filler, 

 road oils, asphalt cements, tars, Portland cement, concrete, steel rein- 

 forcing, and brick. The conference also recommended standard 

 methods of sampling, testing, and reporting test results for these 

 materials. 



One thousand three hundred and forty-five samples were analyzed 

 or tested in the laboratories during the fiscal year. The slight de- 

 crease of approximately 7 per cent as compared with the preceding 

 year was due to an unusually large number of samples of culvert 

 metal tested during that year. 



ROUTINE CHEMICAL TESTING AND INSPECTION. 



Four hundred and twenty-six samples were examined in the chem- 

 ical laboratory. This represents a decrease of about 10 per cent as 

 compared with the last fiscal year, although bituminous materials, 

 the most important type examined in the chemical laboratory, 

 showed an actual increase of 10 per cent. Of the samples examined 

 376 were bituminous materials, 19 metal, and 31 rock, sand, cement, 

 and miscellaneous materials. 



PHYSICAL TESTS OF ROAD-BUILDING MATERIAL. 



The physical laboratory tested 919 samples, a decrease of about 

 6 per cent as compared with the last fiscal year but well above the 

 average annual routine testing. Of these samples 406 were rock and 

 slag, 283 gravel, 173 sand, cla}^, soil, etc., 11 cement and concrete, 

 and 46 miscellaneous. Samples were received from every State in 

 the Union except Nebraska, Nevada, and North Dakota. The more 

 important were as follows: Virginia, 219; Georgia, 68; Connecticut, 

 32; Ohio, 32; Maine, 31; Florida, 31; North Carolina, 29; Indiana, 

 27; Kansas, 27; West Virginia, 26; Pennsylvania, 23; and Vermont, 

 20. The Results of Physical Tests of Road Building Rock in 1916 

 was published as Department Bulletin No. 537. 



