ATMOSPHERIC ELECTRICITY. 101 



Some curious statistics have been collected, especially in Germany, 

 as to the damage done by lightning- flashes. That damage seems to 

 have increased to an enormous extent within the last fifty 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 expla- 

 nation 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 principality 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 the approaching end 

 of the lightning, and was looked upon with favor 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 tact 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 occa- 

 sionally as St. Elue or St. Elme. But it is much more probable, as 

 argued by Dr. F. Piper (Pogg. Ann., Vol. LXXXII, p. 317), 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. 

 He 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 electricity 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, 1 in a pamphlet published 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 his deductions, the 



'"Die gemeinsckaftlicke Ursache der elektriscken Meteore unci des Hagels," 

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



