294 EXPERIMENT STATION RECOKD. [Vol.35 



ing implements, threshing appliances, winnowing and cleaning appliances, 

 appliances in the preparation of crops for the market, appliances for transport 

 of agricultural products, implements used in improvement of land, Konkan 

 implements, mallad (a heavy rainfall tract of Karnatak) implements, hand 

 tools, water lifts, and yokes and hitching. Appendixes are included giving a 

 glossary of vernacular words of crops, the kinds of wood used in the manufac- 

 ture of implements with their scientific names, and vernacular names of different 

 parts of implements with their English equivalents. 



Directory and specifi.cations of plows for tractor use {Farm Machinery, 

 No. 1211 (1916), pp. 22, 23).— This list includes 91 of the types manufactured 

 in the United States. 



Proper use of rams for farm water supplies, W. G. Kibchoffek {Engi/n. 

 News, 75 (1916), No. 10, pp. J,5t, ^58, figs. 2). — The hj-draulics involved in the 

 design of a hydraulic ram system of water supply are briefly presented, to- 

 gether with a specific example. 



Concrete silos, E. S. Hanson (Chicago: The Cement Era Publishing Co., 1916, 

 pp. 174, fiffs. 78; rev. in West. Engin., 7 (1916), No. 2, pp. 78, 79; Engin. News, 

 75 (1916), No. 7, p. 319). — This book represents an attempt to compile and 

 summarize the present available knowledge of concrete silo construction. It 

 contains the following chapters: Why build a silo? what a good silo should be; 

 how concrete meets the requirements ; advantage over other kinds of silos ; 

 size and shape of a silo ; the different types of concrete silos ; the foundation 

 of the silo ; the monolithic silo ; the Polk system ; the Monsco system ; the Reichert 

 system ; other monolithic systems ; the pit silo ; tlie metal lath silo ; the concrete 

 stave silo ; the concrete block silo ; doorways, doors, roofs, etc. ; and how to in- 

 crease the silo business. It is stated that part of the material was drawn from 

 bulletias of the state agricultural experiment stations. 



RURAL ECONOMICS. 



The agricultural element in the population, E. Merkitt (Quart. Pubs. 

 Amer. Statis. Assoc., n. ser., 15 (1916), No. 113, pp. 50-65). — ^Among the con- 

 clusions brought out in this paper, presented at the annual meeting of tlie 

 American Statistical Association, Washington, D. C, December 29, 1915, are 

 that the principal reasons for the decreasing percentage of the total workers 

 employed in agriculture are that the agi'icultural element in the population is 

 becoming more efficient, and that in the readjustment or changes in the metho<is 

 of producing and distributing agricultural products agricultural people now 

 perform a smaller part of the complete operations than was the case formerly. 

 As evidence of the increased efliciency are the facts that the agricultural 

 workers are producing more crops per capita and use a smaller percentage of 

 the total population for the purpose than formerly. 



Another indication of the increased efficiency is the fact that the average 

 number of acres of crops cultivated per agricultural worker is increasing and 

 is accompanied by an increased number of horses on farms per agi'icultural 

 worker and by an increase in the average yields per acre. 



The decrease in the agricultural and rural population in the north Central 

 States is due to a decreased number of farms and to smaller farm families. 



The author states that anything that tends to upset the relationship between 

 the supply and demand of labor in one field of endeavor sets in motion a 

 migration fi-om one part of the country to another or from one country to 

 another, and that the relationships l>etween the rural and urban population 

 are rendered unstable owing to differences in death rate, birth rate, and 

 migi'ation. 



