RURAL ENGINEERING. 891 



compression is transmitted tlirougli a rack and gear to a ribbon wheel, wliich 

 through a -steel ribbon, permits the record point to be moved by a coil spring 

 which is in tension and which is attached to the other end of the guide carrying 

 the needle point. A roll of sensitized paper 10 in. wide and some 100 yds. in 

 length is led through rolls which derive their motion from a sprocl<et wheel on 

 the hub of one of the rear wheels. The reduction of motion is such that each 

 Inch of paper traveled represents 22 ft. of road travel, or 240 in. to the udle. 



It is pointed out as a result obtained from the use of this instrument that 

 light grades are of more importance for good hard roads than for those with a 

 soft surface. Tests showed a greater proportional extra draft for starting a 

 load on hard roads than on soft. 



The tests from which the records shown in this article were taken gave the 

 following drafts in pounds per ton on the different roadways: Hard dirt, 106.4; 

 sheet asphalt, 50; block a.sphalt, 52; Belgian block, 47; and loose sand, 315. 



With reference to the effect of tire width on the draft, the author is of 

 the opinion " that there is a definite law by which the cumulative effect of the 

 width of tire may be measured, and that this law is the equation of a true para- 

 bola, the constants of which vary with the road material. This variation may be 

 sufficient to change the constants for a given width of tire to such an extent 

 that the curve will be convex upward for one material and convex downward for 

 the other." It was also found that the increase in draft on grades is about 20 

 lbs. per ton of load per cent of gi'ade, iri-espective of the road material or 

 its condition or of the tire width. 



"As the increased draft is a constant, and as the draft for the level varies 

 with the road surface, it is evident that the importance of grade elimination 

 depends upon the material of which the road is to be constructed. Referring 

 to the figures previously given for drafts of a wagon on various materials, it 

 will be seen that as 315 lbs. is necessary to haul a ton on a loose sand road, 

 it will require a grade of over 15 per cent to double the draft ; In the case of 

 a hard dirt, a grade of over 5 per cent will be required, while in the case of 

 sheet asphalt a grade of 2i per cent will double the draft, while but slightly 

 over 2 per cent is required on a road constructed of Belgian block." 



Plowing' investigations by the West of Scotland Agricultural College 

 (Impl. and Macli. Rev., 41 {1915), No. 481, p. 72).— The results of tests of the 

 relative merits of the swing and digger plow, as measured by the yield of oats 

 gi'own on i)lats plowed by the two plows, were in favor of the swing plow. 

 It is stated, however, that on account of the dry weather the results are incon- 

 clusive. In comparing the work of the two plows, it is stated that " from an 

 economical point of view the digger plow is far ahead of the swing." 



The rotary tiller or soil milling machine, M. Patitz {Trans. Amer. Soo. 

 Agr. Engin., S {1914), pp. 57-69, figs. 4)- — A description is given of the me- 

 chanical details of the rotary tiller as it is being developed by manufacturing 

 interests in this country. 



Practical implements and machines for potato cultivation, Stkeckeb 

 {MascJiinen Ztg., 13 {1915), No. 5, pp. 11-23, figs. 2.8).— This article describes 

 and illustrates several types of potato planting and cultivating implements. 



Experiments with steel wires, A. J. Werth {Mitt. Ver. Ford. Moorkultur 

 Deut. Reiche, 33 {1915), No. 5, pp. 76-80, figs. 2).— Experiments on Schleswig- 

 Holstein moors showed that steel wire frames were satisfactory for beans and 



peas. 



A comparison of the King and Rutherford systems of barn ventilation, 

 L. J. SJtiTH {Trans. Amer. 8oc. Agr. Engin., 8 {1914), PP- 42-54, f^gs. 3).— The 



