518 



ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



age of routine work in tlic physical laboratory. Tlie samples may 

 be classified as follows: 



Rock 319 



Sand 244 



(iravel 203 



Cement 88 



Slag 55 



Concrete 48 



Brick 



Miscellaneous G3 



Samples were received from 43 States and also from the Dominican 

 Republic, West Indies. Below is given the geographical distribution 

 of samples examined: 



Alabama 



Arizona 



Arkansas 



California 



Colorado 



Connecticut 



Delaware 



District of Columbia. 



Florida 



Georgia 



Idaho 



Illinois 



Indiana 



Iowa 



Kansas 



Kentucky 



Louisiana 



Maine 



Maryland 



Massachusetts 



New Mexico 



Michigan 



Minnesota 



Mississippi 



28 

 11 

 48 



3 

 12 



2 

 10 

 55 

 37 

 11 



2 



2 

 12 



4 

 14 



8 

 21 



3 

 49 

 33 



2 



23 



8 



35 



Missouri 9 



Montana 30 



Nebraska 11 



New Hampshire 1 



New Jersey 15 



New York 5 



North Carolina 31 



Ohio 12(5 



Oklahoma 78 



Oregon 4 



Pennsylvania 44 



South ( 'arolina 42 



South Dakota 3 



Tennessee 15 



Texas 3 



Utah 12 



Virginia 102 



Washington 1 



West Virginia 17 



Wisconsin 35 



Dominican Republic 9 



Total 1,026 



MICROSCOPIC EXAMINATION AND CLASSIFICATION OF ROAD-BUILDING ROCK. 



The petrographic laboratory examined 865 samples of road mate- 

 rials during the year, an increase of almost 27 per cent over the pre- 

 ceding year and well above the average of routine work. Of these 

 samples 339 were rock, 53 slag, 205 gravel, 214 sand, 52 clay, and 2 

 miscellaneous. 



RESEARCH ON DUST PREVENTIVES AND ROAD BINDERS. 



The following investigations have been under way on bituminous 

 materials : 



1. Investigation of the process of refining crude petroleums. 



2. Exposure tests on road oils and asphalts to study the effect of 

 weathering and atmospheric exposure. 



3. Investigation of the effect of so-called w^hite and black alkalies 

 from New Mexico on asphaltic cements. 



4. Investigation relative to the new penetration needle. 



5. Study of density and voids in bituminized aggregates. 



In the investigation of the process of refining crude petroleums 

 seven experimental steam distillations were made, using three typical 

 crude petroleums. From the data collected in this rnanner and from 

 the extensive testing of 187 samples from the experimental refinery 

 a paper on ''Some relations betw^een the characteristics of steam- 



