OFFICE OF PUBLIC ROADS. 743 



covering rather long periods of time are studies of the effects of light 

 and of weathering on various bituminous materials, and the results 

 will be published from time to time as sufficient data are accumulated. 



In connection with the standardization of tests an exhaustive 

 research was made toward the adoption of a standard method for 

 the distillation of tars, and this work will continue through the com- 

 ing year in conjunction with work of a similar nature on other 

 routine tests. Improved apparatus for the extraction of coarse bitu- 

 minous aggregates has been perfected and used to great advantage, 

 and experiments looking toward the perfection of satisfactory appa- 

 ratus for testing the binding value of bitumens have also been 

 conducted. 



The usual winter course of instruction in the chemistry of bitu- 

 minous road materials and methods of testing them was given to 

 five civil engineer students. The need for this special knowledge on 

 the part of engineers has become so evident that the office has adopted 

 the plan of having all its field force detailed to the laboratory, when 

 convenient, for a thorough course of instruction, and, as a result, four 

 of our superintendents of construction and three highway engineers 

 have taken this course. That the value of such a course is appre- 

 ciated by those outside of the office is shown by the fact that already 

 two chemists have been detailed by their respective State highway 

 commissions and received instruction in our laboratory methods. 



During the year five papers prepared by the laboratory force were 

 published either as Government reports or in the proceedings of 

 technical societies, and one other, prepared in the fiscal year 1910, 

 was not published until some time later. The latter was a paper on 

 the " Determination of soluble bitumen," published in the Proceed- 

 ings of the American Society for Testing Materials, and a paper on 

 " The effect of traffic upon macadam roads surfaced w^ith heavy oils," 

 published in the Proceedings of the American Society of Civil Engi- 

 neers. Of the papers prepared in this laboratory one is a popular 

 article on the manufacture, classification, and use of bituminous road 

 materials, two deal with the correlation of laboratory to field results, 

 one is a report of original laboratory research, one is a compilation 

 of definitions, and one contains a description of the methods of 

 examination at present in use in our laboratories. 



The laboratory force participated in the lecture work of the office 

 to the extent of giving one popular talk on road materials at Kuna, 

 Idaho, and delivering two scientific lectures — one before a class in 

 civil engineering at the Iowa State Agricultural College, Ames, Iowa, 

 and one before a class in civil engineering at Cornell University, 

 Ithaca, N. Y. Two papers mentioned in the preceding paragraph 

 were also read before technical societies. 



The demand for specifications covering the various types of bitu- 

 minous binders and bituminous road construction is continually in- 

 creasing, and during the past year 81 copies were issued upon request. 

 Their variety is best shown by division according to the following 

 titles: Petroleum and petroleum products^ 21; refined tars, 20; fluxed 

 native asphalts, 10; construction, 11; oil-mixed concrete, 16; and 

 sulphite liquor, waterproofing compound, and bridge-floor mastic, 

 1 each. These were distributed as follows: California. 1; Con- 

 necticut, 1; District of Columbia, 1; Idaho, 1; Illinois, 4; Indiana. 2: 

 Iowa, 6; Maryland, 3; Michigan, 3; Minnesota, 3; Missouri, 1; Nf- 



