VELOCITY OF ELASTIC WAVES IN GRANITE 65 









TaBLe I. 
Westerly Quincy Rockport 
Fine grain Coarse grain 
SiO: 74.00 70.30 72.86 74.37 
TiO; 0.10 0.31 0.18 0.18 
Al,Os3 13.86 15.10 11.74 12.88 
Fe.C, 1.18 1.58 2.99 0 94 
FeO 0.71 0.99 1.56 1.56 
MnO none 0.04 0.03 0.03 
MgO 0.11 0.50 0.19 0.23 
CaO 0.75 1225 0.14 ORSZ 
Na,O 2.88 3.69 4.36 4.11 
K:0 6.20 5.58 5.28 4.92 
H,0 — 0.09 none none none 
H,0+ 0.31 0.40 0.41 0.31 
CO; none none none none 
P:0s none none none none 
SO; none none none none 
100.19 99.74 99.74 100.05 
TaBLeE II. 
Westerly Quincy Rockport 
Fine grain Coarse grain 
Feidspar 45% 50% 60.10% 59.48% 
(orthoclase) (orthoclase) (mostly (mostly 
Perthite) Perthite) 
Quartz 35% 35% 28.88% 35.14% 
Others 20% 15% 11.02% 5.58% 
(muscovite 15 (muscovite 3 (riebeckite (hornblende) 
biotite 2 biotite 7 aegerite 
magnetite 3) magnetite 3 fluorite 
zircon and titanite) 
apatite 2) 
quartz and feld- quartz and feld- 
spar crystals spar crystals 
range from range from 
1/60 mm to 144 mm to 4 
2 mm in di- mm in di- 
ameter, aver- ameter, aver- 
age 4 mm ca. age 13 mm ca. 

X. Discussion 
La Courtine 
At La Courtine, Maurain, Eblé, and Labrouste® registered seismic waves 
generated by explosions and transmitted through a granitic terrane. 
They recorded longitudinal waves at distances of 5.6 km, 7.7 km, and 
13.9 km. When distances of this magnitude are used, a good velocity de- 
termination can be made with less accurate timing than is necessary with 
shorter distances such as were used in the present work. This advantage, 
however, is offset by the introduction of uncertainty as to the uniformity of 
terrane throughout the range. At La Courtine the presence of both gneiss and 
granite in the path of the waves lessened the certainty with which the veloci- 
ties obtained may be assigned to granite. 
209 
