4 BULLETIN" 257, U. S. DEPARTMENT OF AGRICULTURE. 



Experiment No. 2 (Light Oil — Penetration Method). 



Location: Station 0+35.8 to station 0+58.1=22.3 feet. 

 Area: 44.6 square yards. 



Method. — This section was intended to be a part of experiment 

 No. 1, but owing to the destruction of the barrel markings during 

 storage, a kettle of the light oil was heated by mistake and applied 

 here at an average rate of 1.12 gallons per square yard. It was 

 entirely absorbed during a half hour's standing, after which it was 

 covered with sand and rolled. 



Experiment No. 3 (Heavy Oil — Penetration Method). 



Location: Station 0+58.1 to station 1+65.9=107.8 feet. 

 Area: 215.6 square yards. 



Method. — The apparent failure of experiment No. 1 necessitated 

 a return to substantially the same method as was used in experiment 

 No. 6 at Miami, although the poor working conditions did not promise 

 equal success. The application of hot bitumen was reduced to an 

 average rate of 0.89 gallon per square yard. From station + 58.1 

 to station 1 + 39.0 the actual rate of application was 1.01 gallons per 

 square yard. From station 1 + 39.0 to station 1 + 65.9 rains during 

 the previous night had so bound the surface that the rate of applica- 

 tion had to be reduced to 0.54 gallon per square yard, and little more 

 than a surface treatment was obtained. The sand was applied and 

 rolled as usual. 



Experiment No. 4 (Water-Gas Tar Preparations — Surface Treatment). 



Location: Station 1+65.9 to station 1+95.4=29.5 feet. 

 Area: 59 square yards.- 



Method. — Owing to the postponement of the work from January 13 

 to 29, this section of the road had become completely water bound by 

 rains and heavy traffic. The surface was thoroughly swept with 

 rattan brooms, and water-gas tar preparation No. 1 applied without 

 heating at a rate of 0.25 gallon per square yard and allowed to 

 stand for 24 hours. Water-gas tar preparation No. 2 was then 

 applied at the rate of 0.42 gallon per square yard and allowed to 

 stand for about four hours. By that time it appeared to have reached 

 its maximum penetration and was covered with sand and rolled. 

 By the use of the light tar preparation applied directly to the surface 

 of the rock and followed by the heavier product, it was hoped to 

 secure greater adherence of the bituminous surface than had pre- 

 viously been obtained in strict surface treatment, and at the same 

 time build up a comparatively thick wearing coat. 



Experiment No. 5 (Water-Gas Tar Preparation— Penetration Method). 



Location: Station 1+95.4 to station 3+34.4=139 feet. 

 Area: 278 square yards. 



Method. — The screened-rock course was constructed as usual, but 

 by rescreening the rock the proportion of fine material was consider- 



