Periodical Literature. 19S 



with the idea that total evaporation increases with altitude. The 

 maximum evaporation was shown by the instrument at the 

 second station, 1,100 meters altitude. Above that a gradual and 

 irregular diminution was shown. It may be that the influence of 

 temperature on evaporation over-balances the effects of dimin- 

 ished pressure and air movement. His records, however, refer 

 only to weekly totals, and throw no light on what might happen 

 during a certain portion of the day. 



C. D. H. 



Vegetation and Altitude. Plant World, March, 1909. 



The United States Weather Bureau estab- 

 Evaporation lished, under the direction of Prof. Frank 

 Tests. H. Bigelow, five towers 40 feet high about 



the Reno, Nevada, reservoir in order to 

 obtain data in regard to evaporation. On these towers evaporat- 

 ing pans were located at different points on the reservoir. Evapo- 

 ration from 29 pans was measured every three hours for six 

 weeks. Prof. Bigelow found that the rate of evaporation at the 

 different altitudes seemed to be controlled by the invisible vapor 

 blanket which always overlies any body of evaporating water. 

 He states that in dry climates this vapor blanket above the water 

 will be from 300 feet to one-fourth mile deep, according to the 

 size of the sheet of water. In moist climates it will be deeper 

 and more extensive. In the arid regions of the West it seems 

 probable that this vapor blanket conserves about three-eighths of 

 the water that would otherwise be lost by evaporation. 



C. D. H. 



Monthly Weather Review, Washington, February, 1909. 



SILVICULTURE, PROTECTION AND EXTENSION. 



Professor Wagner, whose book (see F. Q. 

 Obstacles Vol. VI, p. 160) has stirred up a lively dis- 



to cussion on silvicultural subjects, feels 



Natural called upon to further explain and defend 



Regeneration. his pet scheme of the strip selection system, 

 which consists in securing natural regener- 

 ation in narrow strips located on north sides by a kind of selec- 



