320 EXPEEIMENT STATION EECOBD. 



It is shown that air gains and loses heat chiefly by convection. The plant 

 gains heat by convection and radiation, and perhaps by conduction of an in- 

 ternal rather than surface character. The soil gains and loses heat chiefly by 

 radiation. Frosts are generally preceded by a loss of heat from the lower air 

 strata, due to convection, and a horizontal translation of the air followed by 

 an equally rapid and great loss of heat by free radiation. There are various 

 other minor changes which affect the process, but the most important factor is 

 the actual transference of the air and vapor and the removal of the latter as an 

 absorber and retainer of heat. 



The metliods of frost fighting discussed are (1) the use of protective cover- 

 ings, including not only cloth, straw, and the like but also smudges; (2) the 

 direct application of heat by means of such appliances as the improved orchard 

 heaters used successfully in orange groves; (3) mixing the air and thus getting 

 the benefit of the warmer air at the higher levels; and (4) spraying or irrigat- 

 ing, or using sand, as is done in the case of cranberry bogs. The second method 

 is the one which has proved most successful for large scale operations. 



The author concludes that "there is no valid reason, in the light of what 

 has been already accomplished, why at critical periods which may be antici- 

 pated the needed volume of surface air may not be sufficiently warmed and the 

 losses which have heretofore been considered inevitable be prevented." 



The temperature and precipitation of British Columbia, A. J. Connob 

 {Ottawa: The Metcorolopicnl Herince of Canada, 1915, pp. 90, pis. ^). — This is 

 the first of a series of booklets in which " all the data arising from meteoro- 

 logical observations In Canada during the last seventy years or more will be 

 analyzed and published in synoptical form with comment." 



The weather of the year 1912 in Hertfordshire, J. Hopkinson {Trans. 

 Hertfordshire Nat. Hist. Soc, 15 (1915), Xo. 4, pp. 225-238) .—This is a rt-pc.rt 

 based upon a continuation of long-period observations on temperature, precipi- 

 tation, and general weather conditions at Watford, St. Albans, and other sta- 

 tions in Hertfordshire. The principal data are tai)ulatpd and the general 

 weather conditions for each month of the year are described. 



The weather of the year 1913 in Hertfordshire, J. Hopkinson {Tratis. 

 Hertfordshire Nat. Hist. .S'oc, 15 (1915), No 4, pp. 225-258).— This Is a report 

 of a continuation of long-period observations on temperature and precipitation 

 at various places In Hertfordshire, with notes on the weather of each month 

 of the year. 



The climate of Hertfordshire, J. Hopkinson {Trans. Hertfordshire Nat. 

 Hist. Sor., 15 (1915), No. Jf. pp. 195-206, fig. 1). — A brief account is given of 

 the main climatic characteristics of this region as deduced from rainfall ob- 

 servations covering a period of 70 years (1840 to 1909) and other meteorological 

 observations covering a period of 25 years (1SS7 to 1911). Tlie stations at 

 which the principal observations wore made were Bennington, St. Albans, and 

 Berkhamsted. 



The annual rainfall of Scotland and the limits within which it fluctuates, 

 A. Watt (Jour. Scot. Met. Soc., S. ser., 16 (1914), No. SI, pp. 312-319).— The 

 data obtained at 127 stations having unbroken records for 40 years are 

 analyzed. It is shown that " for Scotland as a whole, the average annual 

 rainfall of the driest period of three consecutive years is one-fifth less than 

 the mean annual rainfall." 



Rainfall and vapor tension in western and equatorial Africa, R. CHt'DEAU 

 (Cowpt. Rend. Arnd. Sci. [Paris], 161 (1915), No. 13, pp. 392-395; ahs. in Rev. 

 Sci. [Paris], 53 (1915), I-II, No. 20, p. 509).— The available data on this sub- 

 ject are summarized and discussed. 



