152 OUTLINES OF FORESTRY. 



unless marked differences of temperature exist 

 between neighboring portions of the air. The 

 removal of the forest from any considerable section 

 of country permits such differences of tempera- 

 ture to occur. In point of fact, it has been no- 

 ticed in parts of the world from which the forests 

 have been removed, that the number and severity 

 of hail-storms have undoubtedly increased. 



Destructive hail-storms may therefore be re- 

 garded as one of the evil results which naturally 

 follow the destruction of the forest. 



As regards the supposed protective influence 

 of lightning- or hail-rods against destructive hail- 

 storms, Loomis, in his " Treatise on Meteorology," * 

 writes on page 135 : 



" It has been proposed to preserve the vineyards and valua- 

 ble farms from the ravages of hail by erecting an immense 

 number of poles, armed with iron points, communicating with 

 the earth, for the purpose of drawing off the electricity of the 

 clouds. Multitudes of these hail-rods were erected in Switzer- 

 land, but without the expected success. 



" It is believed that electricity performs altogether a subordi- 

 nate, if not an unimportant part in the formation of hail ; 



* Reprinted, by permission, from " A Treatise on Meteo- 

 rology," by Elias Loomis, LL.D. New York: Harper & 

 Brothers, Franklin Square, 1868. Pp. 305. 



