RURAL ECONOMICS. 491 



" In order for destructive action to become marked the alkali solutions must 

 percolate through the cement work, or at least must penetrate beyftnd the 

 surface. When the action is strictly confined to the surface, as when briquets 

 of neat cement are immersed in a still solution, the tensile strength may be 

 increased. In such cases the expansive action closes up the pores, making the 

 surface more nearly impervious and preventing the alkali from penetrating 

 further. When cracks are started by the expansive action due to alkali salts, 

 wetting and drying, or freezing and thawing, will hasten the destruction of the 

 cement by extending the cracks already started. 



"Any measures that hinder the penetration of the alkali solutions into the 

 interior of the cement will delay the destructive action. For this purpose both 

 soap and aluminum sulphate were tried in laboratory tests and found to afford 

 some protection. The soap, however, in itself had a slightly injurious effect 

 on the tensile strength of the cement. The efficiency of these and of other 

 waterproofcTS is being further studied [by Ihe authors] and results will be 

 reported in a later bulletin." 



The materials of paint manufacture, G. B. Heckel {Jour. Franklin Inst., 

 171 {1911), No. 6, pp. 599-614). — A digest of data regarding the materials 

 used and the processes followed in the manufacture of paint. 



Plumbing" and household sanitation, J. P. Putnam (Garden City, N. Y., 

 1911, pp. 718, pi. 1, figs. 652). — Historical data, theories which have to do with 

 the general subject of plumbing, and practical and theoretical plumbing prob- 

 lems are discussed in this volume, which represents a course of lectures 

 delivered before the Plumbing School of the North End Union, Boston. 



The process of disinfection by che nical agencies and hot water, IIarriette 

 Chick {Jour. Hyg. [Carnbridge], 10 {1910), No. 2, pp. 237-286, dgms. 21).— 

 Studies are reported of disinfection with phenol, hot water, and sunlight and 

 drying. 



A general conclusion reached is that "disinfection, whether by disinfectants 

 or by heat, may be considered analogous to a chemical reaction the velocity of 

 which is controlled by external conditions such as temperature or concentra- 

 tion of bacteria and disinfectant." 



Kitchens and laundries — their planning, arrangement, equipment, and 

 sanitation, W. P. Gerhard {Dom. Engin., Philadelphia Ed., JfS {1909), Nos. S, 

 pp. 62-69, figs. 16; 7, pp. 182-18.',, fig. 1 ; Eastern Ed., 50 {1910), No. 3, pp. 

 61-66, figs. 10; 58 {1910), Nos. 2, pp. 35-39, figs. 5; 3, pp. 63-66, figs. 11; 9, pp. 

 221-225, figs. 11; 5-'t {1911), Nos. 3, pp. 5-'i-58, figs. 10; 7, pp. 178, 179; 8, pp. 

 207-210, figs. 7). — In this exhaustive discussion of the subject hotels and public 

 institutions are considered as well as home kitchens and laundries. 



Chapters are devoted to cooking with diffei-ent fuels and with electricity. 



The text is supplemented by numerous plans and illustrations. 



RURAL ECONOMICS. 



The average mortality among farmers, according to the Bank of Gotha 

 {Intermit. Inst. Agr. [Rome], Bui. Bur. Econ. and Soc. Intel., 2 {1911), No. 2, 

 pp. 138, 139). — The general opinion that farmers are subjected to smaller risks 

 and that mortality among them is lower than for the rest of the population 

 is controverted by tables prepared and based on data collected annually among 

 the adjoining rural population by the Bank of Gotha since 18S0. It is shown 

 that excluding farmers engaged in the manufacture and sale of alcohol, where 

 the death rate is particularly high, " the average mortality of the farming 



