686 EXPERIMENT STATION RECORD. 



" The increase in penetration of a material determined under given con- 

 ditions of temperature and time is, witliin certain limits, almost proportional 

 to the increase in load. For the 100- and 200-gm. loads variations of as much 

 as 1 gm. do not as a rule seriously affect determinations. It is, however, 

 recommended that in all cases the load should not vary more than 0.2 gm. from 

 that desired. 



" In any test, proportionally the greatest number of points penetration is 

 obtained during the first second. In the 5-second test approximately one-half 

 of the total penetration is obtained during the first second. A variation of one- 

 half second may, however, produce an appreciable variation in results. A care- 

 fully calibrated metronome is recommended for securing the proper time control. 

 " Aside from possible variations in neetlles, it is believed that variations in 

 results obtained upon the same material by different laboratories are more 

 probably due to unobserved variations in the methods of preparing the sample 

 and to the control of temperature than to any other causes. It is believed that 

 a study of the penetration of various tyi>es and grades of bituminous materials 

 under a variety of conditions of temperature, load, and time may throw con- 

 siderable light upon their other physical and chemical characteristics, and may 

 serve as a possible means of identifying their origin and method of manu- 

 facture." 

 The authors propose to continue studies along this line. 



A study of West Virginia sands, B. Taylor, R. P. Davis, and A. D. Wil- 

 liams (IF. Ta. Dcpt. Agr. Bill. 7 (IDUf), pp. 32, figs. i5).— This bulletin de- 

 scribes the methods and results of a number of briquette and other tests of 

 \yest Virginia sands which are representative of the river bank and crusher 

 sands of the State. Most of the sands were composed chiefly of quartz and 

 most of the other sands contained a large percentage of cinders. 



" In these tests the bond of the cement was the weaker element with the 

 quartz grains not failing even in the 28-day tests, but the grains in the soft 

 material broke in the 7-day test." The cinders weakened the mortar. "The 

 coarser sands rank far superior in strength. . . . The series of tests indicate 

 the truth of the general law that a gradation of coarse and fine elements is 

 productive of the greatest strength, other things being equal. Where strength 

 is of greatest importance, the sieve analysis curve is of considerable value in 

 selecting the sand. . . . 



" From these experiments it appears that sharp sands show a greater increase 

 in strength than do the others. For instance, crusher sands which have sharp 

 grains improved in rank from 7- to 2S-day tests, while all the other sands have 

 a lower rank in the 28-day test than in the 7-day one. The .strength of the 

 mortar does not bear constant relation to the proportion of cement. Hence, the 

 importance of testing out sands." 



Electricity in agriculture, C. J. Rohreb (Gen. Elect. Rev., IS {1915), No. 6, 

 pp. ^SS-496. figs. 21; Sri. Amer. Sup., 80 (1915), Nos. 2011, pp. 261,-266, figs. 7; 

 2078, pp. 278, 279). — This is a discussion of the application of electrical power 

 to various farm operations. See also a previous and more detailed report by 

 the author (E. S. R., 32, p. 885). 



Economical construction of rural lines, A. S. Hall (Jour. Eleetricitg, S5 

 (1915). No. 23, pp. 4.30-.',.i2, figs. 3). — After pointing out the desirability of a 

 rural load for central stations and describing some important applications of 

 electricity to farming, suggestions are made for methods of construction which 

 it is believed will make it economically possible to give rural service. 



Mechanical plowing in Risaia, A. Takchetti (UAratura Mcrcanira in 

 Risaia. VerceUi: Gallardi tfe I'go, 1911,, PP- 162, figs. 96).— This presents in com- 



