B. K. Emerson on Seebach’s Earthquake in Germany. 407 
were projected, or by the degree of resistance overcome in form- 
ing cracks, as determined by separate experiments. The results 
obtained by Schmidt and Mallet, together with the results of the 
latter's experiments on transit velocity in various rocks, are 
brought together below in comparison with the numbers ob- 
tained by the method we are reviewing, the whole including 
all the reliable numerical results for earthquake elements thus 
ae sted. 
Vibrations which reach the surface of the earth would form 
concentric widening circles, and all points on each circle would 
be shaken at the same instant. These are the isoseistic curves 
of the author (coseismic curves, Mallet). i | 
, then, a perpendicular be drawn from the middle of a 
chord connecting two such points (points shaken at the same 
absolute time, and thus lying in the same isoseistic circle), it 
would pass through the eigeiias ss and the intersection o 
ul 
