288 THE CANADIAN NATURALIST. [Sept. 



The general direction of the vibration, as shown by the times 

 at the different places mentioned above, and by observations of 

 Prof. Winslow, at Cambridge, and by Mr. Douglas, at Quebec, 

 was from north east to south west. The shock must therefore 

 have been propagated from the Laurentian regions north ot the 

 St. Lawrence, into the Silurian and later formations to the south- . 

 ward. This is of interest in connection with the facts already 

 related as to its severity at the edge of the Laurentian formation 

 at Bay St. Paul, and elsewhere. 



It is also deserving of notice, that at Bay St. Paul and Les 

 Eboulements several shocks are recorded; and that additional 

 shocks are stated to have occurred at the latter place on the 26th 

 October, six days after the principal shock. 



It has been observed on previous occasions that the Barome- 

 ter is low at the time of the occurrence of earthquakes, in Eastern 

 America. Dr. Smallwood, has kindly furnished the following 

 table in illustration of this. It gives the state of the Barometer 

 at Montreal, on the days of eleven of the most recent earthquakes 

 felt here. 



Date of Earthquake. Barometer. 



1855. Feb. 8 29.806 



— — 19 29.800 



1856. Jan. 1 30.163 



1857. Oct. 16 29.308 



1858. Jan. 15 30.292 



— Mav 10 29.800 



— June27 29.800 



1860. Oct. 17 29.964 



1864. Apr. 20 29.900 



1870. Mar. 4 30.300 



1870. Oct. 20 29.299 



It will be observed that the Barometer was unusually low on 

 the day of the late earthquake, and according to information 

 kindly sent to Dr. Smallwood from the observatory at Washing- 

 ton, this was very general over the continent. 



It is thus extremely probable, that, whatever the prioiary 

 cause of the movement, its occurrence on the particular day in 

 question, may have been determined by this removal of pressure 

 from the surface of the land. It is further to be observed, that 

 this would place the phenomena in harmony with that general 

 cause to which the frequent small earthquakes on the Eastern 

 Coast of America, were formerly assigned by the writer, namely 

 the removal of material from the land, and its accumulation on 

 the banks off the American Coast, producing unequal pressure and 



