1916] RURAL ENGINEERING. 587 



power per barrel, The following formula may be used for determining capacity 

 and power : 



^ dnS 1 1 , „ 



C=— I jj — ; h,= - and T=C p where 



C=capacity in barrels; (Z=diameter of roll, inches; n=3.1416 ; S=speed of 

 fast roll, revolutions per minute ; i^total length of roll surface, inches ; /=con- 

 stant used=109; 6=barrel=196 lbs.; ?i=inches roll per barrel; p=horsepower 

 per barrel, as 0.4 for plain, 0.35 for collar, and 0.26 for ball bearing ; r=total 

 horsepower for mill," 



Composition of galvanized-wire fencing materials, E. S. Erb and W. Freab 

 (Pennsylvania Sta. Rpt. 19 U, pp. 377-390, pis. 3).— This article reports studies 

 of the composition of more or less well-known wire fencing materials and of 

 newly purchased portions of the principal commercial brands on sale in Penn- 

 sylvania, together with a description of methods of analysis. 



Farm buildings, how to build them, W. E. Frudden (Charles City, lotva: 

 Author, 1916, pp. 63, figs. i55).— This is a booklet of practical information 

 intended for the farmer and rural contractor, covering the construction of 

 general farm barns, hog houses, cribs and granaries, poultry houses, fences, 

 homes, miscellaneous farm buildings, and handy devices. 



Community hog houses, J. B. Davidson, J. M. Evvard, and W. G. Kaiser 

 (loiva Sta. Bui. 166 (1916), pp. 406-458, figs. ^2).— This bulletin enumerates 

 the essential features of an ideal hog house and the advantages and disad- 

 vantages of the community type of hog house, and describes and illustrates the 

 construction of two successful types of community hog houses, namely, the 

 "Iowa sunlit community hog house" and the "semi-monitor roof house". 



The distinguishing features of the Iowa sunlit community hog house are the 

 location of the windows in the roof, thus furnishing direct sunlight to all parts 

 of the house, and low walls used with the idea of reducing cost of construction. 



The distinguishing feature of the half-monitor roof hog house is the arrange- 

 ment and location of the windows. "A row of vertical windows is provided for 

 lighting each of the two rows of pens. The house extends with the long axis 

 east and west, and is not at all adapted to any other direction. When the 

 windows are placed at the right height, direct sunlight will shine into both rows 

 of pens at the same time. If plenty of windows are provided, the pens will be 

 quite thoroughly lighted." 



A previous bulletin by Evvard and Davidson dealt with movable hog houses 

 (E. S. R., 32, p. 284). 



Water supply for the country home, M. K. Snyder (Wash. State Col., Dept. 

 Ext. Bui. 11 (1916), pp. 62, figs. 27).— This bulletin deals with the sanitary 

 a.spects of farm water supplies, purification of farm water supplies, and small 

 water supply systems. 



With reference to source, farm water supplies are divided into rain, surface, 

 spring, and ground waters. The usual precautionary statements regarding the 

 protection of wells and springs are given. With reference to the safe distance 

 from pollution for wells it is stated that "if the earth is reasonably uniform, 

 without any well-defined channels along which the water passes, the safety 

 distance is from 75 to 100 ft. above the source of pollution to from 200 to 250 

 ft. below the source. If there are well-defined channels in the earth, no distance 

 oelow the source of pollution is safe." 



Water purification by mechanical and chemical treatment is discussed and 

 the doubtful utility of small faucet filters pointed out. With reference to 

 small sand filters, it is stated that "the sand layer, at the time of construction, 

 should not be less than about 3 ft. deep and depths greater than 5 ft. are costly 



