B. K. Emerson on Seebach’s Earthquake in Germany. 409 
the distance of this point from the focus of the hyperbola gives 
the time occupied by the wave in passing vertically from the 
center or origin of the shock to the surface of the earth. The 
latter value multiplied by the mean transit velocity already 
obtained, gives the depth of the “centrum” in miles. 
The first of these constants (¢°)—the time of the initial shock— 
is, in this case, easily determined by drawing the hyperbola; 
the second, however—the distance of the center of the hyperbola _ 
from its focus—is not attainable from the lack of observations 
Depth of the Center.—The author compares the depth of cen- 
ter of the Neapolitan earthquake, as given by Mallet, with the 
result obtained above, draws in plate 11 the hyperbola for the 
Rhenish earthquake of 29th July, 1864, from numbers given by 
Julius Schmidt, and, in plate 1, that for the earthquake of 
Veterna hola, using data supplied by the same author. The 
e 
Ratek known for the depth of center of earthquakes. The 
epths are in nautical miles. 
Locality. Date. ulator. Mean. ‘aximum. um. 
Middle Germany, 6 Mar., "72, vy. Seebach, 9°68 11°68 1-76 
Naples, ’ Mallet, 11-765 =: 8125 2-75 
Rhin 64. vy. Seebach : 93 
eo ela, 4 ekg far v. peer 17-(?) 14°16 (?) 
Intensity.—The intensity at the earthquake center of the 
shock or blow which caused the vibrations, is here sought. 
passing out from this center the intensity of vibration must 
grow less as the square of the distance from that center. And 
at the outer limit of the shaken region the intensity of the 
vibrations is approximately the same for every earthquake, 
because this outer limit is determined by the observations of a 
great number of individuals, and indicates only the point 
