214 EXPERIMENT STATION EECORD. 



temperature, radiation, humidity, cloudiness, sunshine, precipitation, wind 

 movement, and casual ])henomena are summarized and discussed. 



Vertical temperature-gradients of the atmosphere, especially in the region 

 of the upper inversion, W. J. Humphreys {Astrophys. Jour., 29 {1V09), iSiO. 1, 

 pp. lJ,-32, jkl. I ; "''v. in Set. Abs., Sect. A—Phys., 12 (1909), No. 135, pp. 131, 

 138). — "After summarizing the present state of our knowledge of the distribu- 

 tion of the vertical temperature-gradient in the atmosphere and the various 

 hypotheses to explain the existence of the upper inversion or isothermal layer, 

 the author proceeds to offer an explanation of the latter, based on consideration of 

 the amount of radiation received by it from the sun and the earth respectively." 



On the mechanical energy of precipitation, H. Reisner ( Met. Ztschr., 26 

 (1909), A'o. 2, pp. 85-87, figs. 2). — Equations and formulas for estimating the 

 energy are given and applied to certain European areas of known rainfall. 



On the influence of forests on rainfall and the probable effect of " deboise- 

 ment " on agriculture in Mauritius, A. Walter (Mauritius: Govt., 1908, pp. 

 54, 2ils. 6, figs. Jjj rev. in Nature [London], 78 (1908), No. 2033, pp. 610, 611; 

 Met. Ztschr., 26 (1909), No. 2, pp. 87, 88). — The forest cover has been reduced 

 from one-third of the total area of the island in 1850 to about one-tenth in 1880 

 and further clearing has occurred since the latter date. A study of the rainfall 

 data, especially from 1860 to 1907, gives " evidence that the cutting of the 

 forests may have had some little effect on the total fall, but has had more 

 effect on the number of rainy days. . . . The rainy days in the districts de- 

 nuded of forests have been decreased by about 30 days per year, but under 

 such conditions that the amount due to these 30 days is only about G to 10 in., 

 whereas the annual variation of total I'ainfall is often GO in. Before the forests 

 were cut rain fell on many calm afternoons, because the presence of moisture 

 transpired by the trees was sufficient by increasing the humidity and decreasing 

 the pressure to cause slight showers. The rain caused in this way is, how- 

 ever, very local." 



The effect of forests on rainfall (Indian Forester, S-'t (1908), No. 10, pp. 

 571-573). — An argument based upon investigations l)y E. Henry is presented to 

 show "that if we wish to maintain the present rainfall of the SA'orld, we must 

 necessarily maintain the present area of forests in the world, or. if we desire to 

 increase the rainfall, we must increase the forest area by afforestation of waste 

 lands." 



Cause and effect of the gradual disappearance of forests on the earth's 

 surface (Indian Forester, SJ^ (1908), No. 10, pp. 600-60.',). —This is a review of 

 an article by Ducamp, setting forth the injury which results from destruction 

 of forests as regards water supply and other physical conditions of the earth's 

 surface. 



It is stated that " the effect on the physical state of the earth's surface of 

 the gradual disappearance of forest growth which is the natural covering of 

 the land, is one which necessarily takes place so extremely slowly that it is 

 A-ery likely to escape observation, or, even when perceived, to have its impor- 

 tance undervalued." 



Deforestation, drainage, and tillage, with special reference to their effect 

 on Michigan streams, R. E. Horton ([Mich. Engin. Soc], pp. 23, pi. 1, figs. 

 6). — In this article an attempt is made to compare present conditions of forest 

 growth, drainage, and tillage in northern and southern Michigan with the 

 primeval conditions in those regions, with especial reference to their effect on 

 the flow of streams. It is pointed out that " arguments from common observa- 

 tions are of little value. Reliable conclusions as to the effect of forests on 

 streams can only be drawn after careful study with full knowledge of the avail- 

 able hydrophysical data." 



