614 EXPERIMENT STATION RECORD. 



parative ease. Two of the chief causes of impure air iu cities are smolie and 

 street dust. The former can l)e greatly reduced by the elimination of steam- 

 power transportation iu lU'ban and densly populated districts, which is asserted 

 to be entirely unnecessary and should have long ago been prohibited. It is also 

 asserted that the accunuilation of street dust is inexcusable from the hygienic 

 standjioint. The heating appliances now in general use are in many cases ob- 

 jectionable because they collect dust and disseminate it thi-oughout the air in 

 houses. Conditions in houses can be Improved by seeing that all stoves and 

 grates are connected with flues. The author is of the opinion that in general it 

 is better to secure ventilation by natiiral means rather than by use of forced or 

 mechanical ventilation. 



The life history of surface air currents: A study of the surface trajec- 

 tories of moving air, W. N. Shaw and R. G. K. Lempfort {Loudon: Wyman 

 d fSoiis, 1D06, pp. 107, pis. 26, flys. 20). — The paths or trajectories of storms 

 are worked out and platted from records of the air movement at a large number 

 of stations in the area passed over by a series of typical storms, and the bearing 

 of the results thus obtained on the movement of air into or out of storm areas 

 and on the associated weather conditions is discussed. 



Progress in the field of water investigation, L. Krauss {Apoth. Ztg., 21 

 (1900), p. SJ/G; al)S. in Chcni. Ztfi., SO {1900), \o. 03, Repert. No. -',6. p. JfO.]). 



Springs in limestone regions and their quality for drinking purj)oses, 

 H. ScHARDT {BuL ^Soc. Neuchittel ,S'ci. Nat., 32 {1903-4), pp. 221-2^2) .—Tlus is 

 one of the reports provided for at the Thirteenth International Congress of 

 Hygiene and Demography at Brussels in 190.''. and discusses somewhat elabo- 

 rately the conditions affecting the drinking quality of waters from limestone 

 areas. The danger of imperfect filtration on account of fissures and under- 

 ground channels is very clearly brought out and a strict examination and con- 

 trol of waters of this kind is shown to be an urgent necessity in order to insure 

 their purity and safety. 



Contribution concerning the purification of water by ozone, D. Rivas 

 {Centbl. Bakt. [etc.] 2. AM., 11 {1906), Nu. 11,-16, pp. 506-517, figs. 6).— The 

 preparation of ozone by means of electrical discharges is described and experi- 

 ments in Philadelphia in which the process was applied in the purification of 

 water are reported. 



The results lead to the conclusion that under favorable conditions ozone not 

 only reduces the general bacteria content of water but also eliminates Bacillus 

 coli communis. It also attacks objectionable organic matter in the water and 

 oxidizes ammonia to nitrate. In water rich in organic matter, however, the 

 germicidal and chemical action is only partial. With such water as is ordi- 

 narily obtainable for a city supply it is believed that very satisfactory results 

 would be obtained by ozonization. 



Control of water purification plants, von Cochenhausen {Ztschr. Angew. 

 Chcm., 19 {1906), Nos. J/S, pp. 19S7-199S ; J,9, j}p. 2023, 2024).— A discussion of 

 processes for removing lime and magnesia from water, and methods of deter- 

 mining combined carbon dioxid. lime, magnesia, and hardness in connection 

 with imrification i)lants. 



A sand filter for the home, R. Fletcher {N. H. Sanit. BuL. 2 {1906), pp. 

 190-198; ahs. in Chcm. Ahs., 1 {1907), No. 1, p. 77).— The making and use of 

 such a filter for purification of water for home use are discussed. The capacity 

 of the filter described is about 40 gal. i)er day. 



