METEOROLOGY. 117 



years." The annual mean temperature, lSSl-1912 (omitting 1882, 1884, and 

 1885), was 48.39°. The ahsolute maxinuim, 18SG-1912, was 99°, July 4, 1911, 

 the al»solute minimum — 20°, Fehruary 10, 1899. 



Temperature conditions at State College are stated to be characteristic of 

 the upland of the region, but not representative of the temperature extremes 

 occurring in the lowlands and small valleys of the vicinity. Consequently the 

 records of the actual occurrence of frost include observations in the adjacent 

 lowlands as well as at the college. These records show that "the average 

 dates between heavy and light spring frosts and the corresponding frosts of 

 the full season for the years, 1888-1912, were : Last killing frost in spring, 

 May 9; last light frost in spring, May 13; fir.st light frost in fall, September 20; 

 first heavy frost in fall, October 2; that is, the average period of growth for 

 plants sensitive to frost was 130 days, the period for more hardy plants 146 

 days. The interval of light frost in the spring averaged only 4 day.s, but that 

 of the fall 12 days. The period of safety for delicate plants is indicated, how- 

 ever, more exactly by the extremely unfavorable years, rather than by the 

 average growing season. In 1910, the interval free from frost lasted only 

 103 days, from May 16 to August 27, and in 1912 for only 108 days, from 

 June 9 to September 27. The shortest interval between killing frosts was in 

 1894, namely, 120 days, from May 29 to September 26. The longe.st interval 

 between killing frosts appears in 1899, namely, 172 days from April 11 to 

 September 30. The period, 1888-1912, has witnessed frost in every month of 

 the year except July. This year's [1913] record indicates that only the period 

 from June 9 to August 27, an interval of only 78 days, has been frost-free." 

 The number of days of effective temperatures for plant growth (with a mini- 

 mum temperature exceeding 42° ) varied from 203 in 1892 to 231 in 1912. The 

 average yearly number of such days was 217. The seasonal (May to September) 

 number was 172. " In 10 years out of the 27 years, 1886-1912, the 90° maximum 

 appeared, if at all, only for a single day at a time; in five other 5'ears, the 

 longest consecutive period was two days ; and only that of August, 1900, pro- 

 longed for seven days, was especially severe." 



Clim.atolog'ical data for the United States by sections (f7. S. Dept. Agr., 

 Weather Bur. Climat. Data, 2 {1915), Nos. 7, pp. 22Jf, pis. 2, figs. S; 8, pp. 224, 

 pis. 2, figs. 10). — These volumes contain, respectively, brief summaries and de- 

 tailed tabiilar statements of climatological data for each State for July and 

 Augiist, 1915. 



Monthly Weather Beview {Mo. Weather Rev., 43 {1915), Nos. 7, pp. 311-376, 

 pis. 20, figs. 3; 8, pp. 377-435, pis. 23, figs. IS).— In addition to weather fore- 

 casts, river and flood observations, and seismological reports for July and August, 

 1915 ; lists of additions to the Weather Bureau Library and of recent papers on 

 meteorology and seismologj- ; notes on the weather of the months ; solar and sky 

 radiation measurements at Washington, D. C, during July and August, 1915, 

 by H. H. Kimball ; condensed climatological summaries ; and the usual climato- 

 logical tables and charts, these numbers contain the following articles : 



No. 7. — Note on the Distribution of Moisture in the Atmosphere, by W. R. Blair ; 

 Tables of Sun Spot Frequencies, 1901-1914, by A. Wolfer ; MistpoefiEer, Uminari, 

 Atmospheric Noi.ses ; Oceanic Noises, Uminari, by T. Terada ; Cirrus Bands and 

 the Aurora, by D. F. Planning ; Eddy Motion in the Atmosphere, by G. I. Taylor ; 

 Nature of the Zodiacal Light, by F. Schmid ; Hourly Pressures for Washington, 

 D. C, 1891-1904 (illus.) ; Note on the Effects of Rain Gage Exposure (illus.), by 

 W. G. Reed ; Distribution of Thunderstorms in the United States, by W. H. Alex- 



