644 SCIENTIFIC RECREATIONS. 



of the ground and descending again. The current of air is directed to the 

 centre ; the cyclone, as mentioned, has a spiral or rotatory movement. 



Thunder and lightning have been, to some extent, described under the 

 head of ELECTRICITY, but some observations may also be introduced here, as 

 storms of that nature appertain to meteorology distinctly. 



Electricity is always present in the atmosphere, and arises from evapora- 

 tion and condensation as well as from plants. As the air becomes moist, 

 the intensity of the so-called "fluid" increases, and more in winter than in 

 summer. Clear skies are positively electric, and when large, heavy clouds 

 are perceived in process of formation in a sky up to that time clear, a storm 

 is almost certain to follow. These " thunder clouds," in which a quantity of 

 electricity exists, attract or repel each other respectively. The cloud attracts 

 the opposite kind of electricity to that within it ; and when at last a tremen- 

 dous amount has been stored up in the cloud and in the air, or in another 

 cloud, the different kinds seek each other, and lightning is the result, accom- 

 panied by a reverberation and commotion of the air strata, called thunder. 



Lightning most frequently' darts from cloud to cloud, but often strikes 

 the ground, whereon and in which are good conductors, such as wet trees, 

 metals, running water, etc. The " electric fluid " assumes different forms 

 " forked," " sheet," and " globular." The second is perhaps the most familiar 

 to us, and the third kind is the least known of all. There are many well- 

 authenticated instances on record in which lightning with the form and 

 appearance of fireballs has entered or struck houses and ships. 



" Fulgarites " are vitreous tubes formed in sandy soils by the lightning 

 in search of subterranean water-courses, for running water is a great 'conductor 

 of electricity.* The fire-ball form of lightning has been known to enter a 

 school-house where a number of children were, and to singe the garments of 

 some, killing others. The ball passed out through a pane of glass, in which it 

 bored a hole, breaking every other pane, however, in its transit. Another 

 instance occurred in which the lightning ran about the floor of a room, and 

 descending the stairs, exploded without doing any injury. 



Lightning, like the electric current of the laboratory, will not always 

 set fire even to inflammable objects. An electric spark can be passed 

 through gunpowder without setting fire to it, and lightning will often shatter 

 the object without firing it. Death by lightning is instantaneous, and in all 

 probability quite painless ; for we may argue from analogy, that as those who 

 have been rendered insensible by lightning have had no remembrance of the 

 seeing the flash which strikes so instantaneously, nor of hearing thunder after 

 it, it is instantaneous in its effects. Besides, the natural attitude is preserved, 

 and the face is usually peaceful and limbs uncontorted after death by lightning. 



There are some curious electrical phenomena, such as St. Elmo's Fire, 

 already noticed under ELECTRICTY ; and in some parts of America, in very hot 

 weather, such a light is perceived to issue from trees as the fire glides 



* " Fulgarites " are composed of melted quartz, and on Mount Ararat many have been 

 found which give a character to the formation of the lesser Ararat. 



