1920J RURAL ECONOMICS. 691 



single i-.vliiHltT, twd-stroke cycle, cnido oil engine. The American machines 

 liad 1, -. anil 4 cylinder engines all of the four-stroke cycle type. 



The Swedish niar-hine plowed three furrows on the hillside and only two in 

 the vlei soil. The plows did not scour owing to the unsuitability of the Swedish 

 steel, which was inferior to tlie American steel in this respect. Considerable 

 diificulty was experienced due to slipping on the hillside. This machine could 

 not cross ditches which were easily crossed by the American macluni's, as the 

 engine and plows were mountetl on one rigid frame. Aside from these dillicul- 

 ties, this tractor did good work on both soils but operated somewhat slowly. 



Two of the American machines gave poor results, and two gave excellent 

 results. One tractor with 22 h. p. engine plowed both hillside and vlei with great 

 si)eed and thoroughness and with a nunimum lo.ss of time due to trouble. A 

 feature of this machine was its low fuel consumption and ability to operate in 

 wet soil. It is noted that the Swedish machine plowed both soils at the smallest 

 cost per acre, this being due to a smalUr total cost for fuel, water, and lubricant. 



Tlie establishing of different seeding; widths with a seeding niacliinc, 

 D. Kl'im)1.kk i.Wultr. Diut. Lanihc. GcseU. Osten., n. ser., 3 {J919), No. J/1, pp. 

 S/i7-3.'>l. fig». ^). — A mathematical analysis of seeder operation and con.struction 

 is given, the purpose being to derive an equation for the adjustment of the 

 seeder shares and wheels. 



Silo selection, F. E. Foglk (Michigan Sta. Quart. Bui., 2 {1920), No. 4, pp. 

 186-190). — The important features of different types of silos are discussed. 



How to build caves and storages for vegetables {Vie Cauipayne, 16 {1919), 

 .\u. 196, pp. :i'fJ-J't6, figs. 2.'t). — Information on French practice in the construc- 

 tion of underground storage rooms for vegetables is given, together with a 

 number of sectional drawings of typical structure;?. 



Disposal of sewage in the Tropics by means of septic tanks and soil 

 purilication, C. A. E. van Leeuwen {Medcd. en Rap., Dept. liurgerl. Opciib. 

 Werkcn Ncderland. Indie, Afd. G, 1919, III, pp. 18, pis. 6). — Tropical practice 

 in the (lisiK>.sal of sewage by small installations is described, and studies of 

 soil and the action in septic tanks are reported. 



It was found that the cholera bacillus was killed after remaining three days in 

 a septic taidc, but that the typhoid bacillus was not. Experience with small 

 septic tanks and sand and stone tilters in Dutch East India is reviewed, and 

 drawings of three sewage disposal systems to care for 15, 50, and 100 people 

 are include<l, the design of which is based upon the disposal of about 25 liters 

 (6.(j gal.) of sewage per capita per day. 



Injury (narcosis) of a sewage purification plant by industrial sewage, 

 KAM.MAN.N aiKl Keim {Gstidhtx. Ingvn., J,S {1920), No. 10, pp. 109-112, fig. 1).— 

 Lalxtratory studies of filters, especially .soil filters and sewage irrigation areas, 

 showed that sewage effluent containing only slight amounts of ethylene trichlorid 

 will seriously imiiair the effectiveness of sewage filters, owing to the resulting 

 F»aralysis of bacterial life, especially in the soil filter areas. 



RURAL ECONOMICS. 



An economic study of small farms near Washington, D. C, W. C. Funk 

 {U. .S. Dept. Agr. Bui. 848 {1920), pp. 19, pi. 1, figs. 6).— Results are liere 

 Itresented which were derived from a study of the organization of 152 small 

 farms in the vicinity of Washington, D. C, most of which were located in Prince 

 (Jeorges County, Md., or Fairfax County, Va. The data, tabulated and graph- 

 ically illustrated, relate to the average distribution of crop area, a sunnnary of 

 the farm business, distribution according to tillable area of farm receipts, 

 exjienses, capital, and labor income, and relation of tenure to type of farming 

 and prolits. 



