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pose ; and experiments were begun in the fall of that year with a pro- 

 duct of the same class containing 70 percent of asphalt materials, and 

 known as "Road Oil No. 7." To secure an effective test of this oil in 

 time for its use the following season, Mr. Flint was sent to Yuma, 

 Arizona, where he made, October 9 to 15, a series of experiments sim- 

 ilar to those of the preceding year, but under conditions much more 

 favorable to a fair trial of the materials in hand. Only .12 of an inch 

 of rain had fallen at Yuma for two and a half months, and the maxi- 

 mum daily temperatures at the time of his visit ranged from 80 to 96 

 degrees in the shade and the daily minimum from 41 to 66 degrees. 

 The earth in the sun where the experiments were made warmed up 

 to surface temperatures ranging from 100 to 120 degrees for several 

 hours during the middle of each day. 



To maintain an effective barrier for 6 days on a fairly level sur- 

 face of very dry. sandy loam it was found necessary, under these con- 

 ditions, to pour a line of coal-tar fourteen times, equal to two or three 

 times a day ; while road Oil No. 7 was poured but three times and road 

 Oil Xo. 8 but once. The road oil last mentioned, containing 80 percent 

 of asphaltic materials, had the disadvantage that it must be heated to 

 run from the vessel used in pouring, and that it was not soft enough 

 to hold the chinch-bugs at the lowest temperatures at which movements 

 of escape might begin. On a surface with a slope of forty-five degrees, 

 an effective barrier was kept up 4 days with road oil X~o. 7 by pouring 

 it seven times, while it took thirteen applications of coal-tar to main- 

 tain an effective line under these conditions for two days only. 



Several other experiments had indeed been made in September, 

 1911, by L. M. Smith, at Coulterville, 111., bringing into comparison 

 road oils Nos. 6 and 7 with coal-tar on the one hand, and with other 

 products of the Standard Oil Company and the Barrett Manufacture 

 ing Co., of Chicago. To make these tests the stubble was scraped from 

 the earth in a wheat field in a way to leave a hard smooth, but some- 

 what irregular surface, upon which the tars and oils were poured in 

 a narrow line, such as one would use in making a barrier around a 

 fields of infested wheat. These lines were all kept up for ten days, be- 

 ginning September 5. The daytime temperatures varied from 78 de- 

 grees to 104 degrees F. by a thermometer placed upon the bare ground 

 in the sun. Several rains fell during the period, some of them heavy 

 enough to interrupt the experiment by covering the lines with dirt or 

 by washing them away. Nevertheless, the results were significant and 

 conclusive. 



To maintain perfect lines it was found necessary to pour ordinary 

 coal-tar forty-one times during the ten days, road oil No. 6 ten times, 

 and road oil No. 7 but four, and these only because of the rains. Still 

 heavier road-oils with 80 percent and 90 percent of asphaltic materials 

 respectively (Nos. 8 and 9), required heating to make them fluid 

 enough for pouring, No. 8 to 130 degrees and No. 9 to 160 degrees. 



