io8 The American Geologist. February, i9oo 
Moreover, all the buildings injured were of light construc- 
tion. In some cases the walls were only one brick thick and 
in a few only half as much. Some of the walls had no bonds. 
In one structure where the part was more solid, a long crack 
has developed parting it from the side wall, but neither has 
fallen. Judging from the appearance presented, little damage 
would have ensued had the buildings been better constructed, 
the motion of the wave-particle not having sufficient velocity to 
displace heavy constructions. 
The causes which led to the concentration of the seismic 
energy on this focus are not obvious, or perhaps discoverable. 
No damage is reported from any of the towns on and near the 
coast. But it is impossible to know at present how a huge 
granite mass like that of San Jacinto, lying in the path of a 
seismic wave may affect its transmission. Refraction may con- 
centrate its energy into a point as a lens collects the light- 
rays to a focus or total refraction may divert it from certain 
spots and converge it upon others with disastrous effect. 
The nature of the rock masses also must have its influence. 
After traversing the long valley or detrital flat from the sea at a 
rate of speed due to the disintegrated condition of the ma- 
terials the velocity of the wave necessarily increases on 
striking the more solid and continuous granite of San Jacinto 
mountain, and with this increase of velocity comes an increase 
of destructive power, which would disappear again on the 
emergence of the wave into the flat country with its discontinu- 
ous strata beyond the mountain mass. 
It must also be remembered that few solid buildings exist 
in the part of the region, which is thinly peopled and conse- 
quently information regarding the facts is inaccessible or frag- 
mentary. No instrumental outfit exists in this part of Cali- 
fornia, though from the continued occurrence of light tremors 
it would be a good region for making .observation and collect- 
ine facts. 
