19161 EUKAL ENGINEERING. 293 



smallest tractor in common use, the 2-plow outfit, may be expected to prove 

 profitable. 



" Medium-priced tractors appear to have proved a profitable investment in a 

 higher percentage of cases than any others. 



'* The life of tractors, as estimated by their owners, varies from 6 seasons for 

 the two-plow to 10^ seasons for the 6-plow outfits. The number of days a tractor 

 is used each season varies from 49 for the 2-plow to 70 for the 6-plow machines. 

 No definite figures on the repair charges for late model tractors can be given ; 

 it would not seem safe, however, to count upon less than 4 per cent of the first 

 cost annually (this representing the average for farm machinery in general). 



" Under favorable conditions a 14-inch plow drawn by a tractor covers about 

 3 acres in an ordinary working day. Under unfavorable conditions large gang 

 plows will cover less ground per day per plow pulled than will the small ones. 

 Two and one-half gal. of gasoline and 0.2 gal. of lubricating oil are ordinarily 

 required in actual practice to plow 1 acre of ground 7 in. deep. The size of 

 the tractor has little influence on these quantities. 



" Plows drawn by tractors do somewhat better work, on the whole, than horse- 

 drawn plows. In Illinois the depth plowed by tractors averages about 1.5 in. 

 greater than where horses are used. Efficient operation is essential to success 

 with a tractor, and proficiency usually can be obtained more cheaply and easily 

 by previous study and training than by experimenting with one's own tractor. 

 With a proficient operator the tractor is a very reliable source of power. 



" The use of the tractor for custom work is usually an indication that the home 

 farm is not large enough to utilize it economically. The doing of custom work 

 with the tractor, on the whole, appears to be a questionable practice, although 

 nearly 45 per cent of machines are used for such work to some extent. 



"A tractor displaces on an average about one-fourth of the horses on the farm 

 where it is used. On a large number of Illinois farms brood mares constituted 

 33 per cent of the work stock before the purchase of the tractor. The use of 

 the tractor increased this proportion only 3 per cent. . . . Both increases and 

 decreases in the crop yields are reported from the use of the tractor, although 

 favorable effects are more common than unfavorable. However, increases are 

 not sufiiciently frequent to warrant a farmer placing much dependence on the 

 tractor in this respect." 



The economics of the farm tractor, E. R. Wiggins (Power Farming, 25 

 {1916), No. 2, pp. 16, J,5, J,8, fig. 1; Farm ImiMments, 30 (1916), No. 2, pp. 58, 

 60, 62, 62 A ) , — The results of an investigation conducted in Nebraska on tractor 

 costs are reported in detail, three systems of tractor farm management being 

 considered, namely, (1) private ownership, (2) cooperative management, and 

 (3) custom operation. 



It is concluded that a study of costs of tractor operation does not entirely 

 indicate the advantages of tractor over horse farming since, while there is a 

 saving in favor of the tractor, the added investment necessary must be consid- 

 ered. " The advantage, however, comes ... in the added work that can be 

 done wiht the tractor, at the same cost, and besides all this, the tractor does 

 not use materials that man can use to reduce the cost of living." 



The proper bearing's for farm tractor uses, C. M. Eason (Farm Machinery, 

 No. 1211 (1916), pp. 26. 27, fig. i).— This article deals with different types of 

 antifriction bearings, bearing loads, bearings for radial loads only, rollers v. 

 balls, and size and capacity of bearing. Roller bearings are favored for tractors. 



Indigenous implements of the Bombay Presidency, G. K. Kelkar (Dept. 

 Agr. Bombay Bui. 66 (1914), pp. Yl+lOO, pis. 26). — This is a general survey of 

 the indigenous implements of the Presidency proper which include plows, har- 

 rows, clod crushers, seed drills, interculturing and weeding implements, harvest- 



