1916] KUKAL ECONOMICS. 391 



part 5, by L. H. Allen, contains notes on estimating ; part 6, by W. J. Titus, deals 

 with the artistic design of concrete bridges ; part 7, by A. M. Wolf, deals with 

 the construction in detail of several types of concrete bridges ; and part 8, by 

 P. Aylett and P. J. Markmann, deals with European concrete bridges. 



How the Forest Service bridg'es the more remote stream, crossings {Engin. 

 Rec, 7S (1916), No. 15, pp. .'(85, 486, figs. -^).— Methods of difficult but inexpen- 

 sive construction as adopted by the Forest Service of the U. S. Department of 

 Agriculture in bridging mountain streams of the Northwest are briefly described 

 and illustrated. 



Keeping the engine in good running order, C. V. Hull (Gas Power, IS 

 (1916), No. 9, pp. 30, 32, 64. 66). — Suggestions are given on the care of the valve 

 system and the timing of valves on farm gas engines. 



[Repair of gas engines], J. F. Hobakt (Gas Poioer, IS (1916), No. 9, pp. 54, 

 56, 58, fig. 1). — Information on the proper use of set screws is given. 



Directory and specifications of gasoline and oil farm tractors (Farm 

 Machinery, No. 1277 (1916), pp. 18-20, 25). — This directory contains specifica- 

 tions for 176 tractors of 98 different makes. 



Directory and specifications of plows for tractor use (Farm Machinery, No. 

 1277 (1916), pp. 26, 27).— This directory contains specifications for 82 plows of 

 18 different makes. 



The development and efficient utilization of animal, steam, electric, and 

 internal-combustion motor plows, A. Wolff (Beitrdge zur Entwicldung und 

 toirtschaftlichen Vcrwendbarkeit von Gespann^, Dampf-, Elektro- und Explo- 

 sions- motorpflUgen. hiaug. Diss., Univ. Giessen, 1913, pp. VIII -{-96). — This 

 report deals with the development of horse-drawn plows, steam, electrical, 

 and motor plows, the extent to which the use of each is justified on the basis 

 of efficiency, the relation of the cost of mechanical to animal work, and of the 

 cost of motor to steam plowing. It is pointed out that in Germany deep plowing 

 may be more cheaply done with mechanical than with animal power ; that in 

 such work the mechanical power works a great saving in expensive animal 

 power, and that more actual work is accomplished per unit of time. 



How to plow a field with a tractor, R. Olney (Gas Poioer, 13 (1916), No. 9, 

 pp. 10, 12, figs. 3). — This is an illustrated description of what is considered the 

 best method of laying out a field for plowing with a tractor. 



Lighting farm buildings, J. L. Mowry (Univ. Minn., Dept. Agr., Ext. Bui. 

 58 (1915), pp. 8, figs. 7). — This pamphlet describes and diagrammatically illus- 

 trates small oil, acetylene gas, and electric lighting systems for farm buildings. 



A simple ice precooling plant, Mary E. Pennington (Proc. Amer. Ware- 

 hotisemen's Assoc, 25 (1915), pp. 266-272, fig. 1). — A simple ice precooling plant 

 designed and tested by the Bureau of Chemistry of the U. S. Department of 

 Agriculture is de.scribed and illustrated. 



" The experimental box ... is 22 ft. 2 in. long by 11 ft. 4 in. wide by 8 ft. 

 10 in. high. The bunker occupies 3 ft. 8 in., leaving the box 7 ft. 6 in. wide in 

 the clear. The wire basket holding the ice is 30 in. wide, inside measurement. 

 The cost of such a box is approximately .$800. The interior of the box was 

 painted and enameled to insure as dry an atmosphere as possible." 



Test records are also given. 



RTJIIAL ECONOMICS. 



Psychic causes of rural migration, E. R. Groves (Amer. Jour. Sociol., 21 

 (1916), No. 5, pp. 623-627).— The author states that "the city furnishes force- 

 ful, varied and artificial stimuli; the country affords an environment of stimuli 

 in comparison less strong and more uniform. Minds that crave external, quan- 



