292 EXPERIMENT STATION RECORD, IVol. 38 



It is concluded that the use of wood or lignite in Tunis for this purpose will 

 depend on the cost of obtaining them. The use of wood is considered an in- 

 centive to clear forest lands for agriculture, and the use of lignite should 

 further its exploitation as a rich local natural asset. 



The cost of using farm motors, I, II (Country Life [London], 41 (1911), 

 Nos. 1060, pp. 8*, 10*, fi(j. 1; lOGl, pp. 8*, 10*, figs. S).— This article summarizes 

 the experiences of a number of farmers and the estimates of a few manufac- 

 turers on the cost of operating different agricultural tractors on different 

 soils, with special reference to English conditions. 



Profitable tractor farming, E. J. Stirniman (Iowa Agr., 18 (1017), No. 5, 

 pp. 215-217, figs. 3). — A tractor survey conducted in nine Iowa counties, namely, 

 Marshall, Boone, Hamilton, Hardin, Story, Humboldt, Pocahontas, Calhoun, 

 and Webster Counties, to which 171 tractor owners responded, is reported. 



It was found that 91.2 per cent of the 171 tractors were considered paying, 

 and 515 horses were displaced, or 0.8 horse per 100-acre farm area. The 8-16, 

 10-20, and 12-2.5, or small-size tractors, constituted 71.9 per cent of the total 

 reported. Fifty-five and five-tenths per cent of the tractors were on farms of 

 less than 281 acres, and 90 per cent of these were successful. It cost from 25 

 to 60 cts. per acre for fuel and oil, plowing at the rate of from 0.69 to 1.16 

 acres per hour. Thirty-nine per cent of the tractor owners were doing custom 

 work and 89.8 per cent of these considered it profitable. Eight and one-tenth 

 per cent of the farm help was displaced on 75 farms. 



Large fireproof barn and silos built of concrete (Concrete [Detroit, Mich.], 

 10 (1917), No. 5, pp. 175-177, figs. 8). — This article describes and illustrates a 

 large concrete barn with twin silos, built near Duluth, Minn. It is stated that 

 the double concrete walls and concrete floors have produced a building which 

 proves a satisfactory stable at a temperature of 40° below zero. 



Small cold storages and dairy buildings, J. A. Ruddick and J. Buegess (Can- 

 ada Dept. Agr., Dairy and Cold Storage Branch Bui. 49 (19^7), pp. 21, figs. 5). — 

 This bulletin describes and illustrates plans for farm dairies, together with ice 

 houses and refrigerators. 



Fruit and vegetable storage structures (Concrete [Detroit, Mich.], 11 

 (1917), No 2, pp. 37, 38, figs. 6). — Simple concrete storage cellars for fruits and 

 vegetables are described and illustrated. 



RUEAL ECONOl^nCS. 



Human food from an acre of staple farm products, M. O. Cooper and W. J. 

 Spillman (U. S. Dept. Agr., Farmers' Bui. 877 (1917), pp. ii).— This publica- 

 tion is designed to give an acre for acre comparison of the protein and energy 

 value of different crops and animal products. The production of live stock 

 products per aci*e was arrived at by assuming the acre to be planted in suit- 

 able food for live stock, in proper proportion to give a balanced ration. 



According to the computations, corn furnishes the most calories per acre, the 

 number being estimated at over 3.000,000. The next highest crop for energy 

 production is sweet potatoes, furnishing 2,800,000 calories. Other products in 

 their order of importance from this standpoint are Irish potatoes, rye, wheat, 

 rice, soy beans, peanuts, oats, beans, cowpeas, and buckwheat. The number 

 of calories obtained from an acre in the production of milk was approximately 

 700,000. The product next in importance among animal products was pork, 

 with approximately 675,000 calories. 



The largest estimated yields of protein per a-cre are from soy beans, beans, 

 and corn. ' 



