MKTEOROLOGr. 147 



explanation of this phenomenon has yet been given; many 

 ingenious theories have been proposed, but as we have not 

 space to detail them for the gratification of the curious, we 

 must refer them to larger and more scientific treatises. The 

 probable cause, however, is electricity. 



IGNUS FATUUS, OR "WILL O* THE WISP." 



This is a nocturnal light, commonly known in this country 

 by the name of " Jack- Lantern:" it is seen floating over 

 marshy grounds, moors, grave yards, and along the margins 

 of rivers, and sometimes has a progressive motion, which is 

 probably given it by the passing breezes. The origin and 

 nature of this meteor have been the subject of many supersti- 

 tious theories and absurd speculations; it has often been 

 ascribed to supernatural causes. The most probable explana 

 tion of it is that given by Muller : he supposes it to be hydro- 

 gen gas which is mixed with phosphorus; and that conse- 

 quently it is nothing more than a phosphorescent light. 



A HALO, 



Is a luminous circle, usually of various and beautiful hues, 

 surrounding the sun or moon during certain conditions of the 

 atmosphere. There are two kinds of halo, depending upon 

 different physical causes. The first are small, their diameter, 

 according to Dr. Brande, not exceeding from 5 to 10, and 

 composed of three or more concentric rings of different colors. 

 " These are usually called coronce; and they appear either 

 when a small quantity of aqueous vapor is diffused through 

 the atmosphere, or when light fleecy clouds pass over the sun 

 or moon." The second kind consists of a single luminous 

 circle whose diameter is about 45. 



A halo of the moon is usually a white circle with its inner 

 edge sometimes tinged with pale red. There is much truth 

 in the remark, that a dense halo close to the moon portends 

 rain. Lunar halos are most frequent, because the sun's rays 



