858 



THE POPULAR SCIENCE MONTHLY. 



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 



IMPULSIVE KUSH DISCHARGE, SO-CALLED DARK FLASHES. 



characteristic features of the phenomenon 

 as brought out in the photograph. We pre- 

 sent herewith another cut which is an excel- 

 lent reproduction of the photograph, and 

 with it an explanation of the peculiar ap- 

 pearances observed in the picture. 



The illustration herewith is to be substi- 



tuted 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 lumi- 

 nous air in diameter six or seven times that 

 of the core. The name " impulsive rush " is 

 from Dr. Oliver Lodge's classifi- 

 cation 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 expos- 

 ure, and the flashes altogether 

 distinct in time and place ; or, a 

 reversal of a flash brought about 

 by the glare from subsequent illu- 

 minations ; 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 atmos- 

 phere. It is needless to add that 

 the negative was carefully kept 

 from alteration or retouching of 

 any kind. 



ALEXANDER McAniE. 



Reasons for Emigration. 



The conclusion of an inquiry made 

 under the direction of our Com- 

 missioners of Immigration upon 

 the causes that incite immigra- 

 tion to the United States is that, 

 except in Russia, where emigra- 

 tion is abnormal, the primary 

 causes are the superior conditions 

 of living in the United States, the 

 fewer hours of labor, the exemp- 

 tion from the exactions imposed 

 by foreign governments upon 

 their citizens, and the general 

 belief that the United States pre- 

 sents better opportunities for ris- 

 ing 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 



