B. K. Emerson on Seebach’s Earthquake in Germany. 411 
the horizontal component increases more rapidly, and thus the 
zone of maximum disturbance will be in a circle at some dis- 
tance from the epicentrum, its position being expressed, for a 
homogeneous perfectly elastic medium, by the equation : 
a@:hir=l: 72 298. 
a=radius of circle of maximum disturbance, 
h=depth of centrum, 
r=distance from centrum to circle of maximum disturbance. 
valuable method, which is especially applicable where Mallet's 
could not be used—in regions visited by earthquakes of slight 
intensity and wide extent, as, possibly, for the regions whose 
centers lie near Montreal and Portsmouth, N. H., and certainly 
or California. For the latter region especially, the ease and 
rapidity with which, by this means, all the elements of an 
earthquake may be obtained, should enforce the important 
