344 THE CANADIAN NATURALIST. [Vol. vii i 



of the St Lawrence valley is concerned. Mr. McLeod informs 

 me that the mean barometer for the week preceding the earth- 

 quake was 29.7564, and for the followiog week 30.0864. The 

 barometer on the Friday before the earthquake at 8 p. m. was 

 29.115, the lowest observed siuce March last; but at 1.50 a.m« 

 on Saturday it was about 29.967, which is very near the mean 

 of November 1876, and also a little above the mean barometer of 

 the place for the whole year ; and on Sunday afternoon it rose 

 to 30.200. It would thus appear that the earthquake was pre- 

 ceded by a low state of the barometer, and followed by one 

 unusually high for the season, and this rapid fluctuation was 

 accompanied with much atmospheric disturbance in the region 

 of the Lakes and the St. Lawrence Valley. The weather map 

 issued by the War Department at Washington for Sunday 

 morning, November 4th, shows a low barometer in the Gulf of 

 St. Lawrence and a high barometer in the Middle States — the 

 area of the earthquake being about half way between the ex- 

 tremes. 



In connection with previous earthquakes it has been observed 

 that the greatest intensity of the shocks appeared near the junc- 

 tion of the Laurentian with the Silurian formations. This 

 would be a natural consequence either of the propagation of 

 vibrations upwards from deep underlying regions through the 

 Laurentian rocks, or from the overlying sedimentary rocks to- 

 wards these older rocks. In the case of the recent earthquake, 

 this appears to have applied chiefly to the border of the Lauren- 

 tians extending round by the Ottawa and Kingston to the Adir- 

 ondacks, as if a wave propagated through the Silurian formations 

 had broken against the southern and eastern sides of the Lauren- 

 tian region, or a shock originating under the Laurentian of these 

 regions had extended itself from them into the Silurian rocks to 

 the south and east. If the prevailing impression stated in the 

 reports, that the vibrations passed from W. to E. or N.W to S.E., 

 is correct, the latter would be the more probable supposition. 

 It is, however, very difficult to attain to any certainty as to the 

 actual direction of the disturbance, and some observers give if 

 as precisely the opposite of that above stated. 



In the present year there have been violent earthquake shocks 

 along the chain of the Andes. The latest of these heard of was 

 that of Lima and Callao on the 9th of October. On the west 

 coast of North America, portions of Oregon and Washington 



