720 EXPEEIMEJSTT STATION EECOKD. 



Using the best available data, the author charts summation zones of the tem- 

 perature and moisture conditions in the United States during the frostless period. 

 In the case of temperature the method used is similar to that of Merriam. 

 The result represents the summations of average or normal daily temperature 

 above 32° F. for the frostless season. " The temperature summation zones 

 cross the continent in a generally west-east direction, being southwardly dis- 

 placed in the regions of the two mountain systems and also to some extent along 

 the Pacific seaboard. Practically all of the area of the United States is char- 

 acterized, according to this chart, by normal temperature summation indices 

 ranging from 3,000 to 13,000. The southern half of the Florida peninsula 

 exhibits still higher indices." 



Charting the average normal daily precipitation at 179 different places in the 

 United States, it is shown that the precipitation lines " tend strongly to take a 

 north-south direction, thus crossing [the] isothermal lines and dividing the 

 countiy into irregular climatic areas each of which might be defined by the use 

 of these two systems of lines." A like result is obtained when the evaporation 

 (for which very inadequate data are available) is similarly charted. 



No attempt is made to trace any relation between the distribution of plants 

 smd the climatic areas indicated by the charts. 



Volcanic dust and other factors in the production of climatic changes 

 and their possible relation to ice ag^es, W. J. Humphreys (U. S. Dept. Agr., 

 Bui. Mownt Weather Observ., 6 {1913). pt. 1, pp. SJf, pi. 1, figs. 4,' Jour. Frank- 

 lin Inst., 176 (1913), No. 2, pp. 131-112, pi. 1, figs. 4; Jour. Wash. Acad. Sci., 

 3 (1913), No. 13, pp. 365-371; Sci. Amer. Sup., 76 (1913), No. 1964, P- 114)-— 

 In these papers the conclusion is reached that "volcanic dust in the high at- 

 mosphere decreases the intensity of solar radiation in the lower atmosphere 

 and therefore the average temperature of the earth, substantially as theory 

 indicates a priori that it should, and this effect has been clearly traced back 

 to 1750, or to the time of the earliest reliable records. Hence, it is safe to 

 say that such a relation between volcanic dust in the upper atmosphere and 

 average temperatures of the lower atmosphere always has obtained, and there- 

 fore that volcanic dust must have been a factor, possibly a very important 

 one, in the production of many, j^erhaps all. past climatic changes, and that 

 through it, at least in part, the world is yet to know many another climatic 

 change in an irregular but well-nigh endless series — usually slight though 

 always important, but occasionally it may be, as in the past, both profound 

 and disastrous." 



Volcanoes and climate, C. G. Abbot and F. E. Fowle (Smithsn. Misc. Collect., 

 60 (1913), No. 29, pp. 24, figs. 3). — Summarizing the results of their studies on 

 this subject, especially in connection with the haze produced by the eruption 

 of Mt. Katmai, the authors conclude that " the transparency of the atmosphere 

 was much reduced in the summer of 3012 by dust from the volcanic eruption of 

 Mt. Katmai, June 6 and 7. 



" Evidence of the dust appeared at Bassour, Algeria, on or before June 19, 

 and at Mt. Wilson, California, on or before June 21. 



" The total direct radiation of the sun was reduced by nearly or quite 20 

 per cent at each of these stations when the effect reached its maximum in 

 August. 



" In the ultraviolet and visible spectrum the effect was almost uniform for 

 all wave-lengths, but was somewhat less in the infra-red. 



" From Bassour experiments, including measurements by 2 methods of the 

 radiation of the sky, it appears that the quantity of heat available to warm 

 the earth was diminished by nearly or quite 10 per cent by the haze. There 



