42 BOARD OF AGRICULTURE. 



they broke through ; happily no one was hurt. The movements 

 of the luminous globe were always slow, and not by jerks. Though 

 bright it was not dazzling, and no sensible heat came from it. It 

 does not appear to have had a tendency to follow conducting 

 bodies, or to have been impelled by currents of air." 



A sufficient number of examples have been already adduced to 

 give an approximate idea, of the nature of these fiery globular 

 masses. While they are not of frequent occurrence, yet they 

 have been seen sufficiently often, and studied with so much care, 

 that their existence as a peculiar form of lightning is abundantly 

 attested. Their cause has been variously assigned. Professor 

 Loomis says, they probably result from "a charge of electricity 

 unusually intense, which forces a direct instead of a circuitous 

 passage through the air." By some they are thought to be 

 agglomerations of ponderable substances in a state of great 

 tenuity, and strongly charged with electricity. 



Whatever may be their composition or their cause, in the slow- 

 ness, uncertainty and peculiar character of their movements, and 

 in the extent of the damage, resulting from their explosion, they 

 rank among the most marvellous objects presented in the whole 

 range of meteorology. 



That form of lightning with which we are most deeply con- 

 cerned presents a long, irregular jagged line of light, resembling 

 the spark drawn from an electric machine. Its zigzag path is 

 regarded as due to the compression of air before the electric 

 fluid, by which greater resistance is produced. When its course 

 is strongly resisted in one direction, it turns aside following the 

 line of least resistance, until the air is again compressed before 

 it, when it turns again as before. The duration of an ordinary 

 flash of lightning as determined by receiving the light of an 

 electric discharge upon a white disc marked with black rays 

 radiating from the centre, the disc being made to revolve witlv 

 great rapidity, has been repeatedly determined to be less than a 

 thousandth part of a second of time. The length of the zigzag 

 path ranges from short spaces to the distance of ten miles. 

 Thunder clouds have been observed of all heights from less than 

 one-fourth of a mile to at least three or four miles. 



Inasmuch as low clouds come in contact with the sides of 

 mountains, and even of high hills, the following interesting in- 

 quiry is suggested. Can clouds from which lightnings are 

 incessantly darting be traversed without imminent danger? 



