1 895.] on Atmospheric Electricity. 471 



have increased to an enormous extent within the last 50 years, and 

 although in cases of this kind statistics may easily be at fault, there 

 seems no doubt about the reality of the fact, which may find an 

 explanation in the partial cutting down of forests in those parts 

 where thunderstorms chiefly occur. When lightning strikes into 

 forests, it selects certain trees by preference. Thus, in the prin- 

 cipality of Lippe, taking the percentage of beeches struck by 

 lightning as unity, that for other trees is as follows : — Oak 48, 

 spruce fir 5, Scotch fir, 33. 



The St. Elmo's fire, a continuous discharge from points and sharp 

 angles, is often observed on board ship and in mountain districts 

 during a storm. Its appearance was considered a sign of tho 

 approaching end of the lightning, and was looked upon with favour 

 by the ancient sailors in the Mediterranean Sea, who gave to it the 

 name of Castor and Pollux. There was another appearance called 

 Helena, a bad omen, which by many is believed to have been another 

 form of the St. Elmo's fire, and the present name has been stated to 

 be a corruption of the word Helena. Some support is given to this 

 view by the fact that the Emperor Constantine built a castle in the 

 Pyrenees, which he named after his mother, Helena, and this castle 

 seems to be referred to occasionally as St. Elne or St. Elme. But it 

 is much more probable, as argued by Dr. F. Piper,* that the word is 

 derived from St. Erasmo, a bishop who came from Antiochia, and 

 suffered a martyr's death at the beginning of the fourth century. Ho 

 seems to have been specially considered the patron of Italian sailors. 

 Churches and castles in Naples and Malta were called St. Erasmo 

 and St. Ermo, and Ariosto describes St. Elmo's fires as St. Ermo's 

 fires. The electric discharge which goes under this name has a 

 different appearance according as it is the positive or negative elec- 

 tricity which escapes, and both kinds occur with about equal frequency. 



Although we have not yet arrived at any satisfactory theory of 

 atmospheric electricity, some progress has been made, and this 

 account would not be complete without a short account of the views 

 taken by men of science on the subject. The number of theories 

 proposed is very considerable. Dr. Suchsland,f in a pamphlet pub- 

 lished in 1886, gives an account of twenty-four, to which he adds one 

 — his own. The year 1884 alone has given birth to four theories. 



We may group the theories according to the origin they assign to 

 the source of energy which is involved in the formation of the electric 

 field. All the work we can perform is either derived from the sun 

 or from the earth's rotation. There is, as far as I know, only one 

 theory — that of Edlund — which makes the earth's rotation in space 

 responsible for the separation of electricities in the atmosphere. But 

 Edlund's views are not tenable in theory, and, even granting hia 



* F. Piper, ' Pogg. Ann.,' vol. lxxxii. p. 317. 



t ' Die Gemeinschaftliche Ursache der Elektrischen Meteore und dea 

 Hagels/ H. W. Schmidt, Halle-a.-S, 



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