954 Recent Literature. [ November, 
such violence that whole settlements were destroyed. At the 
Sandwich islands the sea oscillated at intervals of ten minutes for 
three days.” 
Comparing this wave with the one of 1877 we see that one 
reached Hakodate with a velocity of 511 feet per second, whilst 
the other traveled the same distance at 512 feet per second. 
Other practical problems are the determination of earthquake 
origins and the depth of an earthquake centrum, discussed in 
Chapters x and xı. From Mallet’s calculations the greatest 
(Amer. Jour. Sc., 1872) as being at least fifty miles below the 
surface. 
Under the head of distribution of earthquakes in space and 
time, reference is made to a map which does not appear in our 
Fic. 4.—Webber House, San Francisco, Oct, 21, 1868, showing the effect pio 
duced on an end building. : 
copy of the book. Asan example of the vast area over which > 
which was 
“ but in 
hole 
globe.” Earthquakes chiefly occur in volcanic and mo 
its surface many vast depressions. Some of these saucer- >"; 
lows form land surfaces, as in Central Asia. The majori 
these, however; are occupied by the oceans. 
chiefly occur near the rim of the hollows which have the 
: ogee 
slopes. The majority of earthquakes probably have their org! a 
_ on or near the bottom of these slopes.” 
. -As to the frequency of earthquakes Kluge’s estimate of 4620 
ips | the pa dad 1850 and 1857, averaging nearly 
two a day, 5- 
eee Re ey ee 
