5i8 THE POPULAR SCIENCE MONTHLY. 



ceed farther from the surface of the earth, the potential of points in 

 the air differs more and more from that of the earth, the difference 

 being approximately simply proportional to the distance. Also the 

 electrical density is greater on projecting parts of the earth's surface 

 than on those which are plane or concave. These facts are precisely 

 what we should find to be the case in the vicinity of an irregular, 

 charged conductor ; and they are sufficiently explained if Ave regard 

 the earth itself as charged with electricity varying in density. In 

 fact, observations of the potential of so-called atmospheric electricity 

 are simply " determinations of the quantity of electricity residing on 

 the earth's surface at the place of observation." (Professor Everett, 

 in Deschanel's "Natural Philosophy.") 



In the Rocky Mountains electrical storms are of frequent occur- 

 rence. They consist of electrical displays without precipitation of 

 rain, hail, or snow. Usually, though not always, the sky is overcast. 

 In February, 1880, a remarkable electrical excitation was manifest at 

 Boulder, Colorado. The miners were unable to kindle fire in the 

 stove till eleven o'clock in the morning, every attempt to touch the 

 metal about the stove resulting in a severe electrical shock. With 

 every strong gust of wind the manifestations were more marked. 

 Similar reliable evidence comes to the writer from other parts of Colo- 

 rado. Long's Peak, an isolated mountain, 14,271 feet high, is noted 

 for these peculiar electrical manifestations. The density of electricity 

 on the peaks, projecting so far above the general level of the earth's 

 surface, is greater than elsewhere ; hence they possess a power to dis- 

 charge like points on an electrified conductor. The air and aqueous 

 vapor become surcharged with electricity ; and only a slight condensa- 

 tion, sufficient merely to form clouds without rain, serves to produce 

 discharges of lightning. With heavy gusts of wind the charged air 

 is removed, and a fresh supply is provided into which the peak again 

 pours its electricity. 



In view of these facts, the theory is submitted as worthy of con- 

 sideration that the earth itself is the seat of those disturbances that 

 manifest themselves in atmospheric electricity. Fluctuating currents 

 ebb and flow through the confining walls of this immense reservoir of 

 cosmic energy. These follow naturally from the great changes in 

 temperature to which the earth's crust is subjected ; from those seis- 

 mic disturbances occasioned by vast internal convulsions ; from im- 

 measurable local strain and compression, the result of upheaval and 

 contraction. The earth, unlike the moon, contains still a vast store of 

 unexpended energy ; and in the ebb and flux of its mighty internal, 

 contending forces, and the bending and swaying of its magnetic lines 

 of force, in obedience to the magic wand of the sun, there is ample 

 room for the generation of those comparatively feeble forms of energy 

 that manifest themselves in the electrical disturbances of the air. 



