20 Proceedings of Royal Society of Edinburgh. [sess. 
Fig. 4 shows the disturbance in the barograph curve, which 
appears to have commenced at about 5’5 minutes after four, 
attained its maximum effect at about 9'*5, and ended at about 
12'*5 past four. The oscillations in the column of mercury must 
have been caused by more than one distortional wave ; and it is 
interesting to note how the disturbance, which commenced in this 
instrument about half a minute behind that of the declination 
magnetograph, reached its maximum effect fully one minute after 
the maximum effect is recorded in declination magnetograph. The 
oscillations of the column as photographed would correspond to a 
fall of mercury to about *07 inch. 
[Summary. 
