A. C. Twining on the Earthquake of Octoher, 1870. 51 



tn all observed times of the end^ if expressly so given, 

 l^-six seconds has been deducted for the begiiini)ig, as above. 

 Wherever no mention is made of the period in the shock to 

 which the observation applies, the times stated in the notices 

 respectively have been inserted in the table without change, as 

 being the presumed time of the beginning. 



An inspection of this table discloses no considerable north- 

 and-south movement. A nearly east-and-west progress is that 

 which appears most consistent with the aggregate of times. In- 

 deed it presents itself as the only one at all consistent with a 

 uniform and regular progress. Nor is there discovered in the 

 table any decisive indication of a change of direction as between 

 the east and the west of the AUeghanies ; but the various ac- 

 counts, so far as they go, indicate the very reverse. Thus the 

 direction of N.E and S.W., noted at Brunswick, was accurately 

 N. 10° E. at Harvard Observatory, while it was N.N.E. at New 

 Haven, and almost identically the latter also at Chicago. But 

 at Cleveland and Detroit it is described as E. and W., and at 

 Burlington, Vt, N. and S. One account from Boston makes it, 

 incorrectly, N. W. and 8.E., and another from Hartford the same 

 at the latter place. 



The best approximate result appears to be that the earth- 

 quake made progress from about E. 6° N. to about W. 6° S., at 

 the rate of one hundred and sixty miles a minute, being six 

 minutes and a half from St Johns to Chicago ; while snrjyris- 

 ingly, the ordinary direction of the subordiiiate undulation was 

 about N. by E. But there was not absolute regularity of rate 

 in any single direction. The times at Cambridge, at Albany 

 and at New Haven compared together, disclose appreciable devi- 

 ations from the general regimen of the table ; and the same is 

 probably true with respect to the Cleveland observation. Un- 

 fortunately the latter was not checked by comparison with a 

 standard time-piece, — neither, as is probable, was the Owen's 

 Sound observation. That at Cincinnati does not purport to be 

 more than a loose approximation. 



It appears by observations of Prof. Hough at Dudley Observ- 

 atory, obligingly furnished me by him, that the principal shock 

 was observed at 11'* IS"", being a few seconds in duration, but 

 that a tremor continued for at least a minute. No doubt there 

 exist, at various localities not heard from, many observ^ations 

 recorded or distinctly remembered. It is desirable yet to have 

 them communicated to this place, or to some one elsewhere, by 

 whom they will be made available. 



In fact while this article is in press, I am furnished through 

 the favor of H. Paton, Esq., of the Montreal Telegraph Co. at 

 Quebec, with the following important statements by Mr. Eobert 

 MeCord, the operator who made inquiries immediately after 



