688 EXPERIMENT STATION RECORD. [Vol.41 



warmer water, and that In general the variation in temperature during the 

 irrigation season may cause a variation of 80 per cent in the rate of seepage 

 losses. 



The small irrigation pumping plant, W. L. Powees and W. J. GiLMOEii: 

 (Oregon Sta. Bui. 160 {1919), pp. 16, figs. ^).— This bulletin gives general infor- 

 mation on the planning and construction of a small irrigation pumping plant. 



Testing aggregates in the field, F. H. Jackbon (17. S. Dept. Agr., Public 

 Roads, 2 {1919), No. 15, pp. 11-13, figs. 5).— An outfit of field apparatus for test- 

 ing aggregates in the field is described and illustrated, which has been devel- 

 oped recently by the Bureau of Public Roads. The field equipment so far de- 

 veloped consists of the following units : 



One set interchangeable stone screens, wltli screen plates having perforations 

 8, 2J, 2, li, 1, I, ^, and i in. in diameter; 1 set interchangeable sand sieves, of 

 10, 20, 80, 40, 50, 80, 100, and 200 mesh ; 1 circular spring scale having a ca- 

 pacity of 30 lbs. and sensitive to 0.1 lb. ; 1 straight spring balance having a 

 capacity of 200 gm. and sensitive to 1 gm. ; 1 demountable cubic foot box ; 1 

 ordinary camera-folding tripod ; 1 250-cc. graduate ; 1 strip of screen wire about 

 22 in. in length and 5 in. high ; and 2 canvas bags about 18 by 18 in. in size. 

 The total outfit weighs approximately 18 lbs. The apparatus for making screen 

 analyses weighs approximately 10 lbs. and may be packed in a space measuring 

 17 by 8 by 6 in. 



Ultramicroscopic examination of disperse colloids present in bituminous 

 road materials, E. C. E. Lord {Jour. Agr. Research [U. S.}, 17 {1919), No. 4, pp. 

 167-176, pi. 1, fig. 1). — In this article, a contribution from the Bureau of Publi* 

 Roads, U. S. Department of Agriculture, the author describes the method and 

 apparatus employed in the ultramicroscopic analysis of bituminous road ma- 

 terials, and reports the results of a number of examinations to determine the 

 various colloidal materials contained in different types of bitumens. These 

 bitumens were separated into two groups, the first containing clay as colloidal 

 material, and the second in which this mineral matter was replaced by car- 

 bonates, sulphates, and acetates of copper. Iron, zinc, and lead. On examin- 

 ing solutions of the second kind under the ultramicroscope it was found that 

 the copper carbonate salts had been largely reduced to red cuprous oxid accom- 

 panied by an enormous colloidal dispersion, while with the remaining salts the 

 reduction was much less complete or entirely lacking and the development of 

 colloids correspondingly less. 



" It may be stated, therefore, that the colloidal capacity of the second group 

 of materials taken as a whole was dependent largely upon the degree of chemi- 

 cal reaction between the bitumen and the salts employed, while in the first 

 group this supporting value was related more directly to the physical character 

 of the bitumen. A comparison of the duplicate counts . . . indicated that a 

 maximum variation of less than 10 per cent was attained in samples of the first 

 group, while In the second group, the results were, on the whole, less con- 

 cordant, owing largely to the greater dispersion of colloidal matter. In con- 

 clusion, it may be stated that the accuracy of this method for counting colloidal 

 particles In bituminous solutions depends chiefly upon accuracy in construction 

 and calibration of the cell employed, as well as upon the proper consistency 

 and optical purity of the supporting liquid." 



Eflaciency of bituminous surfaces and pavements under motor truck traffic, 

 P. HUBBAED {Munic. and County Engin., 56 {1919), No. S, pp. 98-100).— This Is 

 a general review of experience on the subject, in which It is stated that " main- 

 tenance by the Bureau of Public Roads [of the U. S. Department of A?rlcul- 



