Page:Popular Science Monthly Volume 43.djvu/878

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der F. Chamberlain, Worcester, Mass.; (I) Economic Science and Statistics—Manly Miles, Lansing, Mich. Treasurer: William Lilly, Mauch Chunk, Pa.


A Correction.—Owing to some defect, the cut on page 459 of the August number of the Monthly, intended to illustrate a peculiar form of lightning flash, fails to show the PSM V43 D878 Impulsive rush discharge aka dark flashes.jpgImpulsive Rush Discharge, So-called Dark Flashes. characteristic features of the phenomenon as brought out in the photograph. We present herewith another cut which is an excellent reproduction of the photograph, and with it an explanation of the peculiar appearances observed in the picture.

The illustration herewith is to be substituted for the illustration with the same legend on page 459 of The Popular Science Monthly for August. The flash was photographed by the writer at Blue Hill Observatory, and was one of the most intense flashes he has ever seen. To the eye it appeared as a straight core of dazzling light, with a jacket of luminous air in diameter six or seven times that of the core. The name "impulsive rush" is from Dr. Oliver Lodge's classification of lightning discharges. The so-called "dark flashes" can be distinctly seen branching out from the core. Briefly, these may be the result of previous exposure, and the flashes altogether distinct in time and place; or, a reversal of a flash brought about by the glare from subsequent illuminations; or, a reflection from the lens (although a plain view lens was used), or an absorption effect connected with chemical change in the gases of the atmosphere. It is needless to add that the negative was carefully kept from alteration or retouching of any kind.

Alexander McAdie.


Reasons for Emigration.—The conclusion of an inquiry made under the direction of our Commissioners of Immigration upon the causes that incite immigration to the United States is that, except in Russia, where emigration is abnormal, the primary causes are the superior conditions of living in the United States, the fewer hours of labor, the exemption from the exactions imposed by foreign governments upon their citizens, and the general belief that the United States presents better opportunities for rising to a higher level than are offered at home. Information on these points is usually furnished by friends or relatives who have preceded the intending emigrants and have established themselves here. It is estimated that nearly sixty per cent of the immigrants who land in our country come on prepaid tickets or money sent by friends