The Arizona sentinel., 1886-08-07
LIGHTNING STROKES.
A Plausible Explanation of the Remarka
 ble Increase of Thunder-Storms.

Karsten, Weber and others have proved
 that the number of damaging strokes oi
 lightning has considerably increased
 during the last fifty years, and this in-
 crease can not be explained by the theo-
 " that, owing to the growing number
 of houses, factories, etc., the number oi
 lightning strokes increased proportion.
 ately; to the contrary, this number
 ought to decrease, as every building,
 even when not protected by a lightning.
 rod, effects an equilibrium of the oppo-
 site electric potentials, and therefore the
 number of lightning strokes ought rela. ! lively to decrease with the relative num-
 Der of buildings. This, indeed, is
 proved by the fact that in the space oi one year among one hundred thousand
 buildings there occurred but thirteen
 cases of lightning stroke in cit
 ies, against twenty-three strokes
 on buildings in the country. We, there
 fore, have to take this natural phenom.
 enon from another point of view, and
 to consider the ratio of damaging or
 other strokes to the number of buildings
 in a certain district. This ratio, called
 by the German naturalists bIitzgetalY
 Changer from ightning), increased in
 the kingdom of Bavaria from 1844 to
 1882 three-fold (according to records of
 insurance companies even five-fold),
 and other countries show the same in.
 crease.
 As in nature each phenomenon must
 have its cause, the question arises: To
 what cause is due the above-mentioned
 facts? And this question not only is of
 scientific interest, but also of great
 practical importance. A great many
 theories have already been advanced to
 explain this phenomenon; among oth-
 CTS that, owing to the decrease of the
 woodland, houses are more and more made the projecting points of certain
 area, and therefore attract the light nlng; bes des, this decrease effects a greater rise in temperature in summer, and, in consequence, more nu- merous thunder-storms. Others find the cause of it in the large increase of such constructions as gas and water works, weather-cocks, etc. But this theory does not explain why, especially country houses, which commonly lack these kind of construc. tions, are mostly exposed to danger from lightning. Admitting that these causes may to some extent explain the increase of danger from lightning, they are not sufficient to fully show the sur prising increase of strokes during so short period. There must be more general and fundamental cause. Through what can the electrical in- density during a thunderstorm be so strongly increased that larger mum, Der of lightning strokes pass over to the earth than was the case heretofore? Il is not so much the increasing number of thunder-storms as their greater force which produced the danger
 As the main cause we now point our the enormous increase in the last fifty years of factories, railroads, steamboats in short, of all constructions filling the atmosphere with smoke, va DOTS, particles of dust of every description. When we consider that every day thousands of locomotives, thousands of steamers go around the earth; that thousands of factories of all kinds daily emit enormous quantities of smoke, vapor and dust into the air; that, especially in cities, the large num- Der of houses produce immense quan. titles of smoke and dust, the assertion will not seem incredible that there is certainly one hundred times the smoke, dust and gases absorbed in the atmos- phere that there was fifty years ago. Already with the naked eye the impure state of the atmosphere may be noticed. Go through the coal districts of Man. chester, England, through those of Pennsylvania, through the city of Pitts burgh, and you will notice a layer of | vapor constantly lowering over them; the air is filled with foul gases, and l every object is more or less covered | with the settling particles of dust.
 The conditions being established, We have to consider theIr relations to the violence of thunder-storms. To give the reader a better conception of this relation we will briefly discuss the theory of the thunderstorm and the origin of electricity thereby developed. Friction is now generally accepted to be the cause of the electricity in thunderstorm. Friction between air and particles of ice (accord. ing to Luvine) or between air and mole. eules of water (according to Andries) is the main cause of that electricity. When besides these factors particles of dust are filling the atmosphere the development of electricity is highly increased. It is he election of steam and ashes common o the phenomenon which causes the attending it to assume m exceedingly violent character. That he pyramid of Cheops is rendered cleo rical by the whirling dust of the desert nay here also be mentioned. It is noth- ng but the friction of the grains of sand ,n the surface of the pyramid that causes electricity to originate.
 The author of this essay claims that he rapid, enormous and lasting devel- 'pment of electricity during thunder storms can not be otherwise explained han by purely mechanical cause anal lgous to the mechanical force of the hv- tro-electrlcal machine. Now, as our at nosphere contains so much more dust han in former years, the fact must be # great influence regarding the inten- ity of electrical phenomena during from the same reason ng are explained volcanic eruptions. That this increased force of thunder torms must manifest itself in the great r violence and more dangerous charac- CT of lightning strokes will be evident o the reader. But there is another ause to be mentioned. It is an estab- lshed fact that air containing solid par lcles has conducting power in regard o electric currents tar superior to that f pure air. In our day, therefore.