METEOROLOGY WATER. 517 



and evidence is strong tliat the cutting away of tlie forests has had nothing to 

 do with the creating or the augmenting of droughts in any part of tlie world. 



"(2) Precipitation controls forestation, but forestation has little or no effect 

 upon precipitation. 



"(3) Any local modification of temperature and humidity caused by the 

 presence or absence of forest covering, the buildings of villages and cities, etc., 

 could not extend upward more than a few hundred feet, and in this stratum of 

 air saturation rarely occurs, even during rainfall, whereas precipitation is the 

 result of conditions that exist at such altitudes as not to be controlled or 

 affected by the small thermal irregularities of the surface air. 



"(4) During the period of accurate observations, the amount of precipita- 

 tion has not increased or decreased to an extent worthy of consideration. 



"(5) Floods are caused by excessive precipitation, and the source of the 

 precipitation over the central and eastern portions of the United States is the 

 vapor borne by the warm southerly winds from the Gulf of Mexico and the 

 adjacent ocean into the interior of the country, but little from the Pacific 

 Ocean crossing the Rocky Mountains. 



"(6) Compared with the total area of a given watershed, that of the head- 

 waters is usually small and. except locally in mountain streams, their run-off 

 would not be sufficient to cause floods, even if deforestation allowed a greater 

 and quicker run-off. Granting for the sake of argument that deforestation 

 might be responsible for general floods over a watershed, it would be necessary, 

 in order to pre^ ent them, to reforest the lower levels with their A'astly greater 

 areas, an impossibility unless valuable agricultural lands are to be abandoned 

 as food-producing areas. 



"(7) The run-off of our rivers is not materially affected by any other factor 

 than the precipitation. 



"(S) The high waters are not higher, and the low waters are not lower than 

 formerly. In fact, there appears to be a tendency in late years toward a 

 slightly better low-water flow in summer. 



"(9) Floods are not of greater frequency and longer duration than formerly." 



Climatic variations: Their extent and causes, J. W. Gregory (Ann. Rpt. 

 Smifhsn. Inst., 1908, pp. 330-354). — This article discusses the general uniform- 

 ity of climates in the past, exaggerated estimates of climatic changes, the rela- 

 tion of glaciation to local climatic variations, and causes of climatic variations. 

 The author thinks it " probable that variations in climate, which have been 

 established on adequate evidence, can be accounted for by differences in atmos- 

 pheric circulation, due to different distributions of land and water." 



Variations in climate, F. A. Forel (Arch. Set. Phys. et Nat. [Geneva], Jf. ser., 

 28 (1909), Xo. 9. pp. 299-302).— On the basis of data reported by Briickner and 

 Hellmann, the author concludes that it appears that if there is a variation of 

 long periodicity in rainfall it is neither universal nor continental, but is 

 regional. 



On the dynamics of climatic variations, H. Arctowski (Compt. Rend. Acad. 

 Sci. [Paris], l',9 {1909), A'o. 26, pp. 11,11. ]',t8; ahs. in Rev. Sci. [Paris], //8 

 (1910), I, No. 2, p. 60). — This is a brief account of studies more fully reported 

 elsewhere (E. S. R., 22, p. 313), which indicated the occurrence of immense 

 waves of excess or deficiency of heat which are not influenced by topographic 

 conditions such as the existence of high mountains. 



Annual variations in the amount of water in the Norwegian North Sea 

 in its relation to varying meteorological conditions, yield of crops, and the 

 fishery industry in Norway, B. Helland-Hansen and F. Nanseis^ (Iiitcrnat. 

 Rev. Gesani. Ili/drohiol. u. Hydrog., 2 (1909), No. 3, pp. 331-361, fif/s. 11; ahs. in 

 Naturxc. Rundschau, 2J, (1909), No. 52, pp. 661-663).— A uniform and direct re- 



