784 ANNUAL. REPORTS OF DEPARTMENT OF AGRICULTURE. 



154 were tars, oils, and other dust preventives and road preservatives, 

 114 were limestones, G7 each of granites and sandstones, and 172 trap 

 rocks; while tlic remainder consisted of almost every known road 

 material, including 46 samples of slag. The Oflice has been making a 

 thorough investigation of slag during the year, and has ascertained 

 much in regard to its road-building qualities. Through ofTicial request 

 this Ollice received and tested 1 60 samples of rocks from England for 

 the road authorities of Great Britain. We have also received and 

 tested 1 62 rock samples from the state geologist of the State of Wash- 

 ington. The samples received have come from fortv States and Ter- 

 ritories of the United States, from the District of Columbia, from 

 Cuba and Porto Rico, from Canada, and from England. Among the 

 States sending in samples, those sending the largest numbers nave 

 been: Washmgton, 164; Pennsylvania, 70; Georgia, 63; and New 

 York, 52. A great many samples of materials have been tested m the 

 District of Columbia, sent in through some one of the government 

 offices and amounting to about 220 in all. Of the last number, 105 

 samples were tested for the Isthmian Canal Commission and con- 

 sisted chiefly of rubber hose to be used in the canal construction. 

 Samples have been tested at the request of the state highway commis- 

 sions and state geological surveys of Delaware, Illinois, Louisiana, 

 Maine, ]\Iichigan, j\Iinnesota, New York, Oklahoma, Pennsylvania, 

 Virginia, and Washmgton, the engineering department of the District 

 of Columbia, the park commissioners of Chicago, and the city officials 

 of eight other cities, besides the county officials of numerous counties 

 throughout the country. In addition to these, the Office has tested a 

 large number of materials for different branches of the United States 

 Govermnent, both in the District of Columbia and in the field, such as 

 the Reclamation Service, the United States Geological Survey, the 

 Bureau of Chemistry, and the Isthmian Canal Commission, as men- 

 tioned above. The Baltimore and Ohio Railroad, the Pennsylvania 

 Railroad, and the Cleveland, Cincinnati, Chicago and St. Louis Rail- 

 way have also had a number of samples tested in this Ofl&ce for them. 



INVESTIGATION OF DUST PREVENTIVES AND ROAD BINDERS. 



During the past year the work of the Office relative to the investiga- 

 tion of the problems of dust prevention and road preservation has 

 advanced rapidly, and many useful data have been secured which have 

 been of great practical benefit to those who have sought information 

 on this subject. It should be said that the desire for such informa- 

 tion is almost universal among road builders, and that at present the 

 great majority of settled communities in this country are facing the 

 realization that rapid destruction of their roads under modern traflfic 

 is inevitable unless immediate and active measures are taken to meet 

 these problems. Letters are being constantly received by the Office 

 from aU parts of the country asking for advice regarding the character 

 and method of the application of dust preventives and road binders 

 best suited to meet local requirements. To furnish such advice it has 

 become necessary to increase both the working force and equipment 

 of the chemical laboratory and to harmonize it with the Division of 

 Engineering in such a manner that the two, while separate divisions, 

 will act as a single working unit. The manner in which this has been 

 accomplished will be shown in the following description of the work 

 of the laboratory. 



