NEW PRACTICE. 



297 



of low pressure which forms with the earth a nearly spher- 

 ical condenser. The auroral display in the distant North is 

 believed to be due to the fact that this rarified air space, on 

 account of the low temperature prevailing in those frigid re- 

 gions, lies nearer to the earth's surface than elsewhere, giv- 

 ing rise to visible phenomena. The pointed contour of leaves 



n 



CHAPTER VIII., FIG. 84. FIVE DEGREES BELOW ZERO AND A LONG WAY TO GO. 



has suggested to some their adaptability as electrical con- 

 ductors. Indeed, there are many phenomena in Nature that 

 make it seem reasonable to suppose that electricity may play 

 an important part in the life of the plant world. The experi- 

 ments so far made have had in view the intensification of the 

 natural electrical currents over the face of the soil growing the 

 experimental vegetation. For this puqwse an insulated wire 



