1919] METEOROLOGY. 209 



observations showed that the trouble evidently lay with the closing of the 

 containers. The margin of the lids in the process under examination is painted 

 wiiii a mixture containing flour or starch which fills up the spaces between the 

 Interlocked edges when the cans are closed. A greater leakage In the cans con- 

 taining pears ami plums ihan in those containing peaches ami apricots is con- 

 sidered by the authors to be due to the greater solvent action upon the starch 

 jelly of the juice of pears and to a less degree of plums, and that consequently 

 a different sealing mixture should be employed. An alternative plan is sug- 

 gested of allowing the tins to cool after processing, in a current of filtered, 

 sterile air and, when cold, paiuting the joints with a lacquer varnish. 



METEOROLOGY. 



Frost and the growing season, W. G. Rekd (U. S. Dept. Agr., Atlas Amcr. 

 Agr., pt. 2, Sect. 1, 1918, pp. 12, fiys. 33). — This atlas contains mai>s, charts, 

 diagrams, and descriptive notes dealing with dates, distribution, and condi- 

 tions favoring killing frosts in the United States, variations in the length of 

 the growing season, and suitable planting and harvesting dates. 



Discussing the season available for plant growth, it is stated that " in gen- 

 eral the length of period In which the chance of killing frost is small enough 

 to permit profitable agriculture is, depending on the locality, between 15 and 

 50 days less than the average number of days without killing frost." 



A selected list of references to literature on frost is given 



The measurement of atmospheric pollution, J. S. Owens (Quart. Jour. Roy. 

 Met. Soc. [London], U (1918), Xo. 187, pp. U9-170, figs. 4).— This article dis- 

 cusses the investigations undertaken by the British Advisory Committee on 

 Atmospheric Pollution, describes the methods used, summarizes the results ob- 

 tained, and calls attention to some of the unsolved problems. 



It is stated that the results of three years' observations, 1914 to 1916, have 

 beeu compiled and that a fourth year's results are about ready for publication. 

 During the earlier years, observations were made largely in cities, only one 

 station being in the open country. In the more recent observations, another 

 country station has been added. The author is of the opinion that the value of 

 the investigations would be increased if there were more country stations, 

 properly distributed so as to give comparative figures for country air and the 

 air of cities. 



In general, the results show that the air deposits are greater in winter than 

 in summer, although the proportion of dust as compared with products of 

 combustion are greater in summer than in winter. The amounts of sulphate 

 and chlorin were also highest in winter, but the amount of ammonia appeared 

 to bear no relation to the season. The effect of the wind was apparently ob- 

 scured by other influences. Among the unsolved problems referred to are the 

 relation of atmospheric pollution to disease and bacterial content of the air, 

 the vertical distribution of Impurities, and various factors governing the deposit 

 of floating matter in the air. 



[Observations on aerology] (U. S. Mo. Weather Rev. Stop. 13 (191S), pp. 81, 

 pi. 1). — This supplement contains the following articles: Free-air Data at 

 Drexel, Nebr., and Ellendale, N. Dak., Aerological Stations. April to June, 191S, 

 Inclusive, by W. R. Gregg; and Notes on Kite Flying, by V. E. JakL 



Daily river stages at river gauge stations on the principal rivers cf the 

 United States, 1917, A. J. Henry (U. S. Dc}>t. Agr., Weather Bur.. Daily Hirer 

 Stages, 15 (1917). pp. 2S6).— This is the fifteenth part of the series of river 

 gauge readings maintained by the Weather Bureau. 



