688 EXPERIMENT STATION RECORD. t Vol. 36 



ing material and the relation between the degree of purification and mean time 

 of contact is given, together with the results of tests on fine and coarse, shallow 

 and deep filters. 



Theoretical laws and tabular data are derived which are suggested for use 

 in the design of sewage purification systems. The laws indicate " that the puri- 

 fication should not even theoretically be directly proportional to the mean time 

 of contact. The relations given involve only one constant a [oxygen avidity 

 constant] which Is dependent jointly on the nature of the sewage liquor and the 

 method of purification adopted. ... It is the numerical measure of the rate at 

 which the sewage pollute is oxidized when it is present in unit concentration." 



The equations and tables " give mathematical expression to the fact . . . that 

 the size of the plant required to give a specified degree of purification increases 

 very greatly per unit increase in the percentage purification as the latter itself 

 increases. . . . Given the flow, it has been shown that the mean time of contact 

 is proportional to the liquid content of the purification plant, and this in turn 

 depends on the biological conditions obtaining inside the filter and on the physi- 

 cal nature of the filtering medium." 



RURAL ECONOMICS. 



Proceedings of the ninth Bural Life CJonference {Alumni Bui. Univ. Va., 

 3. ser., 9 (1916), No. 4> PP- in-^dS). — This volume contains abstracts of the 

 papers read at the ninth annual conference held at the University of Virginia 

 summer school, in 1916, and relating principally to rural school and church 

 problems. 



A rural survey of Lane County, Oregon, F. C. Ayek and H. N. Morse ( Univ. 

 Oreg. Bui., n. ser., 13 {1916), No. 14, pp. 109, figs. 32). — This survey relates 

 primarily to the rural and educational conditions found in Lane County. 



[Rural reforms in the organization of Spanish agriculture], G. Fernandez 

 DE L&. Rosa {Bol. Agr. T6c. y Econ., 8 {1916), Nos. 85, pp. 41-50; 86, pp. 157- 

 166; 87, pp. 221-230; 88, pp. 318-324; 89, pp. 396-405; 91, pp. 583-593) .—The 

 author discusses some of the causes for the lack of progress in Spanish agri- 

 culture, and advocates the federation into a national organization of all 

 agencies working for agricultural improvement. 



Semi-centennial history of the Patrons of Husbandry, T. C. Atkeson 

 {New York: Orange Judd Co., 1916, pp. XII-{-364, P'«- 24)- — In this volume, are 

 recounted the activities of the Patrons of Husbandry from the initiation of the 

 order in 1865 to date, together with statements regarding its principal officers. 



History of the state agricultural and mechanical society of South Caro- 

 lina, W. A. Clark, W. G. Hinson, and D. P. Duncan {Columbia, S. C: The 

 R, L. Bryan Co., 1916, pp. XXII+S06, pis. 15).— This volume gives the history 

 of the society from its foundation in 1839, and describes its activities and the 

 men connected with it as officers. 



[Agricultural law of New York] {N. T. Dept. Agr. Bui. 83 {1916), pp. 

 1955-2145). — There have been brought together in this bulletin the laws of 

 the State which affect agriculture. 



The federal farm loan system, H. Myrick {New York: Orange Judd Co., 

 1916, pp. 239). — The author explains the various provisions of the Federal 

 Farm Loan Act and gives the full text of the act together with amortization 

 tables. 



The farm mortgage handbook, K. N. Robins {Garden City, N. Y.: Double- 

 day, Page d Co., 1916, pp. XIII +241). —The author describes the methods used 

 by institutions dealing in farm mortgages in granting the mortgage and in its 

 sale to the public. He points out some differences between the placing on sale 

 of farm mortgages and those of other types. 



