70 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



peratures, but much more the centrifugal force of the earth's 

 rotation, in consequence of which there exists at the points 

 of maximum velocity, during the night as well as the day, a 

 continuous upward current, of aspiration, of the trade or polar 

 current drawn to this region, and that this air, with the moist- 

 ure contained, must again descend. This may only take place 

 in the polar latitudes, toward which it moves, and which it 

 finally reaches in its normal west-southwest direction, also 

 by force of aspiration, as compensation for the air drawn 

 from those regions. 3 (7, September 30, 1872, 949. 



INFLUENCE OF FORESTS OX EAIN-FALL. 



The question as to the influence exercised upon the amount 

 of rain-fall throughout the year by the presence or absence 

 of forests, is beginning to excite much attention, and numer- 

 ous communications on the subject make their appearance in 

 the scientific journals. M. Lemoine, in a paper read before 

 the British Association, remarks that the existence of any 

 influence of this kind must be considered extremely doubtful. 

 In the basin of the Seine it has been shown that forests, as 

 compared with soil coated with grass, have no peculiar influ- 

 ence upon the water-courses. The real function of forests, 

 in his opinion, consists in their protection of tlie soil by pre- 

 venting the earth from being carried away, and in their re- 

 tarding the flow of torrent waters. In fact, in the Alps, the 

 presence of forests prevents the formation of torrents, and 

 the replanting of woods extinguishes torrents already exist- 

 ing ; although, in many cases, merely turfing the soil produces 

 the same effect. 



In illustration of the influence of vegetation in retarding 

 evaporation from the soil, an experiment was adduced which 

 consisted in sinking two cylindrical jars of the same size into 

 the ground to the depth of four inches, leaving them project- 

 ing one inch above the surface. One of these was placed in 

 a newly cleared plot, and the other where it was partially 

 but not completely protected by the bushes. The same 

 amount of water was placed in each jar, and at the expira- 

 tion of five days it was found that the evaporation from the 

 jar in the open grounds had been more than twice that from 

 the one which was covered. 18 A^ September 6, 1872, 637. 



