670 ME. MALLET ON THE TEANSIT-VELOCITT OE EAETHQHAKE WAVES. 
experiments disclose. They prove to us that, in an earthquake shock of given original 
power, the vibrations will have the largest amplitude when transmitted in the line of the 
lamination, but may be propagated with the greatest velocity in du’ections transverse to 
the same, assuming in both cases the rocJc solid and unsliattered. 
In the following Table XI. the general results are deduced, and the mean campres- 
sions for each of the rocks calculated, and finally the moduli of elasticity are obtained 
in pounds and in feet ; the specific gravities adopted in calculating the latter being those 
given in the body of the paper, as follows : — • 
Weiglit of a prism 1 foot 
long and 1 inch square. 
sp. gr. 
lbs. 
Hardest slate 
. . 2-763 
1-1992 
Softest slate 
. . 2-746 
1-1918 
Hardest quartz 
. . 2-656 
1-1528 
Softest quartz 
. . 2-653 
1-1515 
Mean for slate 
. . 2-7545 
1-1955 
Mean for quartz 
. . 2-6545 
1-1522 
General mean for both rocks 
. . 2-7045 
1-1739 
The load on the unit of surface (1 square inch) at which the elastic limit of the rock 
is passed, and that at which it is finally crushed, together with the modulus of cohesion 
or resistance to compression, are also given, and will be useful to the engineer and 
architect. In the last column the value of my own modification of Poncelet’s coetfi- 
cient T,. (la force vive de rupture) is calculated in foot pounds, and represents the 
relative work done at fracture in each case. 
