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THE POPULAR SCIENCE MONTHLY. 



POPULAR MISCELLANY. 



Report upon the Charleston Earth- 

 quake. The United States Geological Sur- 

 vey, according to a communication from 

 Messrs. Dutton and Harden in " Science," 

 has received reports relating to the Charles- 

 ton earthquake from more than sixteen 

 hundred localities, giving a much larger 

 amount of information than has ever before 

 been collected concerning any one earth- 

 quake. A considerable proportion of the 

 reports were in answer to a printed list of 

 questions which had been sent out, to direct 

 attention to the most distinct and significant 

 features of the phenomena. The first point 

 to receive attention is the magnitude of the 

 area affected by the shocks. The earth- 

 quake was felt in Boston, near Lake George, 

 and at two points in the Adirondacks, at 

 several places in Ontario, Michigan, and 

 Wisconsin (at La Crosse, nine hundred and 

 sixty-seven miles from Charleston, the most 

 remote point within the United States which 

 has given a positive report), in some of the 

 Florida Keys, in Cuba, and in Bermuda, a 

 thousand miles from Charleston. The area 

 within which the shakings were marked 

 enough to attract considerable attention, 

 would be somewhat more than circumscribed 

 by a circle of a thousand miles radius. The 

 movement might, however, have been de- 

 tected, by instrumental observation, over a 

 much greater area. There are some large 

 tracts within the area which show compara- 

 tively feeble intensity. The most conspicu- 

 ous of them is the Appalachian region. This 

 fact is of interest in its bearing on the sup- 

 position that mountain-ranges serve as bar- 

 riers to the propagation of earthquakes. 

 Another minimum area was in Indiana and 

 Illinois ; and it nearly corresponded with 

 the area in which a considerable earthquake 

 occurred on the 6th of February. The co- 

 incidence is curious, if not significant. At 

 nearly all places within about two hundred 

 and fifty miles of the center the energy of 

 the shock was very great. Coming nearer 

 to the center, the intensity increased on all 

 sides, with differences in kind as well as in 

 degree. " The phenomena characteristic of 

 the epicentral area cease with something 

 like abruptness as we radiate away from 

 the epicentrum. The central phenomena 



I are those produced by shocks in which the 

 I principal component of the motion of the 

 earth is vertical. Proceeding outward, 

 these predominating vertical motions pass, 

 by a very rapid transition, into movements 

 of which the horizontal component is the 

 greater, and in which the undulatory mo- 

 tion becomes pronounced." The rapidity of 

 these transitions, or the shape of the inten- 

 sity-curve into which they may be translated, 

 is supposed to be dependent upon the total 

 energy and depth below the surface of the 

 shock. The distance from the epicenter to 

 the point where the rate of decline of the 

 intensity is greatest, is simply proportional 

 to the depth of the focus, and is the same 

 whether the energy be greater or less. This 

 gives a rule for estimating the depth of 

 the focus. Applying the rule, we have a 

 computed depth of twelve miles, with a 

 probable error of one or two miles, for the 

 focus of the principal shock at Charleston. 

 There is reason for beliving that none of 

 the great earthquakes of the last one hun- 

 dred and fifty years have originated from a 

 much greater, and few from as great, a 

 depth. The city of Charleston was situated 

 at from eight to ten miles outside of the 

 area of maximum intensity. Had the seis- 

 mic center been ten miles nearer to it, the 

 calamity would have been incomparably 

 greater than it was. The shocks were also 

 probably made easier for the city by the 

 loose nature of the soil and quicksands over 

 which it is built. The time-data have not 

 been fully worked out, but it is thought that 

 they will give a speed of propagation ex- 

 ceeding three miles a second a rate which 

 " will probably prove unexpected to Euro- 

 pean seismologists." 



Some Popular Errors about the Eski- 

 mos. Mr. John Murdoch has exposed, in 

 the " American Naturalist," a few popular 

 errors in regard to the Eskimos, some of 

 which have found their way into Hovelaque 

 and Hcrve's recent book on "Anthropology." 

 Polyandry is not common among them, as 

 is asserted there and by Bancroft, but is 

 very rare, if it exists noticeably at all. Es- 

 kimo houses are seldom, if ever, holes dug 

 in the earth, as the French authors say, but 

 wooden, turf-covered lodges, built sometimes 

 over an excavation of only moderate depth, 



