690 ■ BXPERIMENT STATION RECORD. [Vol. 4S 



Galvanized culverts, L. G. Carmick {U. S. Dept. Afjr., Public Roads. S 

 {1920), No. 2.'), pp. 26-29, fig. 1). — Experiments on the value of the method of 

 testing the galvanizing of. metal culverts by chemical analysis of one or two 

 small pieces cut at random from the culverts are reported. 



It was found that there is a great lack of uniformity in the coating on the 

 different parts of a sheet, which may amount to as much as 50 per cent of the 

 average for the sheet. This is taken to indicate that little reliance can be 

 placed on the results from tests of one or two small pieces. In order to secure 

 an adequate idea of the spelter coating on a shipment of culverts it is con- 

 sidered necessary to take quite a large number of samples. 



Comparative tests of the hydrochloric acid-antimony chlorid and the lead 

 acetate methods of testing for spelter coating showed that when the acid 

 method was used with 1-minute immersions the results were much too high. 

 When the time was reduced to 30 seconds, the results were remarkably 

 accurate, more so than those given by the acetate method. 



Economics of the farm tractor, C. E. Alleed {Tenn. Farmer, IS (1920), No. 

 7, pp. IJ/S, IJflf, l/fG, 148, 156, 158, 160, fig. i).— Average data based upon reports 

 of tractor owners in Tennessee are summarized. With reference to the rela- 

 tion of size of farm to the size of tractor, it is estimated on the basis of the 

 number of 14-in. plows pulled that for 200-acre farms a 3-plow tractor is the 

 most desirable, and for farms of from 201 tc 750 acres of crops, the 4-plow 

 outfit is the best. Other economic factors are considered. 



Influence of the tractor on use of horses, L. A. Reynoi-dson (U. S. Dept. 

 Agr., Farmers' Bui. 109S {1920), pp. 26, figs. 7). — This reports the results of the 

 personal experience of 191 tractor owners in seven corn belt States on farms 

 varying in size from 80 to 1,640 acres. 



Of the 141 farms upon which tractors had been in operation for a year or more 

 the greater number ranged in size from 141 to 220 acres and from 221 to 300 

 acres. Five large tractors were found ranging in size from 8 to 12 plows and 

 in age from 8 to 12 years. All other tractors ranged in size from 2 to 6 plows. 



It was found that the number of horses disposed of on 141 farms averaging 

 346.5 acres, on which tractors had been used for a year or more, was 2.5 per 

 farm. The average number of tillable acres per horse increased from 26.5 to 

 38.5 after the purchase of the tractor. Nine operators out of 191 displaced 

 horses entirely on plowing, disking, and harrowing. Only 16 operators alloweil 

 their hor.ses to stand idle while the tractor was in use. The number of horses 

 displaced by the tractors on these farms was governed by the number it was 

 necessary to retain for corn cultivation and other work current at the same 

 time which the tractor could not do. The horses remaining on these farms are 

 doing about 75 per cent of the tractive work and tractors the remainder. 



The tractor was used for an average of 29 10-hour days per year on the home 

 farm, no record of the amount of custom work done being obtained. A 3-plow 

 tractor on these farms did the work of 8.5 horses in plowing, disking, harrow- 

 ing, and harvesting. After purchasing the tractor the average size of the farms 

 was increased by 22 acres, or 6J per cent. 



Report of motor tractor plowing trials at the Elsenburg School of 

 Agriculture (Union So. Africa Dept. Agr., Local Ser. No. 86 (1918), pp. 16, pis. 

 10). — Trials to determine the efficiency of four American tractors and one 

 Swedish tractor for plowing are reported. Each tractor was required to plow 

 12 acres of hillside stubble land consisting of coarse sandy loam to a depth 

 of at least 5 in., and 6 acres of virgin sandy vlei land to a minimum depth of 7 in. 



The Swedish machine weighed 9,000 lbs. net, while the American niachin<>s 

 varied in weight between 2,800 and 5,000 lbs. The Swedish machine had a 



