410 BK. Emerson on Seebach’s Earthquake in Germany. 
Middle Gurus? 3305-2 
aples, 1252°6 
Rhinelan 1577°3 
Veterna hola (Hungary), 1612°5 
It follows that the intensity of an earthquake is, as a rule, pro- 
portional to its area, and that earthquakes of great intensity 
and limited area originate at a comparatively small distance 
below the surface. 
Transit Velocity—The true average transit velocity of the 
four earthquakes under discussion, as found by the author, are 
given in the table below, together with the results obtained ex- 
Patiinetially by Mallet, at Killiny Bay and Holyhead, for the 
2 ol velocity in different rocks by the explosion of mines 
eee oaths 
Meters per second. Intensity. 
Middle Germany, 742°0 3505-2 
Naples, 259°7 1252°6 
Rhineland, 567°6 1577°3 
Hungary, 206° (?) 1612°5 
In wet sand, 25174 
“ granite much jointed, 398°16 
“ compact granite, 507°36 
“ quartzite and schist, 37916 
One of the results of Mallet’s experiments at Holyhead—that 
the transit velocity increases with an increase in the intensity 
of the initial shock—is brought out clearly by the comparison 
in the table above of the initial intensity with the transit ve- 
locities of the first three earthquakes discussed. 
The form of the Centrum.—One of the most interesting and, 
at first sight, most startling deductions of the author, relates to 
the form and position of the area in which the shock originated. 
If this area had been, as has been heretofore assumed, spherical 
and of small dimensions, the region of most violent action (in 
overturning buildings, &c.) would have been in a circle around 
the e epicen centrum whose radius would have been 8’8 nautical 
This is deduced from an interesting theorem given by 
Mallet* The vibrations reaching the earth at the epicentrum 
will have of course the deceit ae but the horizontal 
_ component will then be zero, and as one passes out from the 
: aaa although the intensity of if the vibrations diminishes, 
* Brit. Assoc. Rep., 1858, p. 101. 
