1919] RURAL, ENGINEERING. 887 



having the engine oiled and cooled so that it can run all the time at 50 per 

 cent to full load, if we are to secure good fuel economy." 



With reference to size of tractor, the author is not in favor of the small 

 tractor as an economical investment but rather favors the use of horses for 

 small farms instead. He is of the opinion that the machine should be as large 

 as one man can operate easily and that can be run over roads, through gate- 

 ways, and over bridges with 9 ft. overall width and 14,000 to 16,000 lbs. weight 

 as the outside limits. 



Controlled tests of tractor labor, E. Rabate (Yie Ayr. et Rurale, 8 {1918), 

 No. 2, pp. 27-29). — Plowing tests on light sandy and siliceous clay soils with 

 eight tractor plowing outfits are reported. Test plats were 280 meters long by 

 40 meters wide. The tractors varied in power from 12 to 30 h. p. and in weight 

 from about 2,800 to about 6,000 lbs. The plows consisted of from two to four 

 bottoms. 



The tests showed that better results were obtained with three plow bottoms 

 than with two larger plow bottoms covering an equal width. The largest volume 

 of soil was turned by a 20-h. p. tractor per unit of area plowed and per unit 

 of fuel consumed. This outfit used a 3-bottom plow and worked to a depth of 

 19 cm. (7.5 in.). The nest best results were given by two 16-h. p. tractors 

 with 3 and 2-bottom plows, working to depths of 17.2 cm. and 18.5 cm., re- 

 spectively. The most powerful tractor with a 4-bottom plow gave only medium 

 results as regards fuel economy and volume of soil turned per unit area, but it 

 stood second with reference to area plowed per hour. 



Traction on bad roads or land, L. A. Legros {Jour. Inst. Mech. Engin. [Lon- 

 don], 1918, Nos. 3, II, pp. 55-158, pis. 40, figs. 54; 4, II, pp. 159-194; abs. in 

 Sci. Abs., Sect. B— Elect. Engin., 21 {1918), No. 246, p. 211).— This is a report 

 of an extensive study and analysis of tractor and truck drives for hauling over 

 roads and agricultural land. 



With reference to the 4-wheel drive, it is concluded that " for the transport 

 of goods over bad roads on gradients, varying from 1 in 15 on roads in which 

 the tires sink 2 to 3 in. in depth to 1 in 5 on hard roads with bad surface, and 

 for speeds varying from 1.5 miles per hour on grades to 12 miles per hour on 

 fairly level roads, the 4-wheel drive tractor has great advantages over the 

 ordinary 2-wheel drive tractor." 



With reference to chain-track tractors, " it can be safely said that where a 

 track can be found 7 ft. wide which does not present rocky obstacles over 

 10 in. high, whether over sand, ash, clay, marsh, snow, or ice, on the level, or 

 on gradients up to 80 per cent, the chain-track tractor has proved itself 

 capable of traveling and performing useful work beyond the capacity of ani- 

 mal haulage. For this reason the chain-track tractor may be expected to oc- 

 cupy a position of ever-increasing importance in the development of new 

 countries, and in places where it is necessary to transport machinery and 

 stores over roadless country many miles from the railway. . . . 



"One featue that is particularly remarkable is the small amount of power 

 lost in compressing soft marshy land under the feet of the track-chains. A 

 very visible alteration of the appearance of a marshy surface due to the prints 

 made by the track feet may, for example, only involve an expenditure of power 

 which is but slightly greater than that required for hard ground, whereas the 

 effort involved in walking over the same soft surface may be many times 

 greater than that of walking on the hard road." 



Test of a disk pulverizer. C. Claeou {Prog. Agr. et Vitic. {Ed. VE fit-Centre), 

 39 {1918), No. 15, pp. 343-350. figs. 3).— Several tests of a disk harrow with six 

 disks for vineyard cultivation are summarized briefly, the general trend of 

 158071°— No. 9—20 7 



