126 LOUIS VESSOT KING 
The principal stress-differences in the rock specimen are from (3) 
(i) 77-23 = —2(e—A+B/7’) 
LAGI AN Cis a Re pea 
aes eee Ras an 
(ii) 7-00 = —4pB/ 7? =P | ae " (13) 
(iii) 66—# = —2n(e—A—B/?) 
se 0 3 pe 20 act dO 
=P} ee) nee at 
The radial displacement U at the outer surface of the rock specimen 
is given by 
_@ rte 
Cook Co b? 1-—o¢ ( ) 
b 2 1-+¢ 1+, na 
and the longitudinal extension per unit length is given by 
: pum clatate) (Warez) 
ngs BA lg Gute Wed Seen Se (15) 
2e@ I+o¢ 1+ 5 
The radial displacement U’ at the outer surface of the nickel-steel 
jacket is given by 
OIE A SEN o 
cm 6G 1—b/ce (1—0)(1-+0’)(1+8) ug 
and the longitudinal extension per unit length is given by 
U! 
Os Ole (17) 
§ 4. DISCUSSION OF EXPERIMENTAL RESULTS 
In order to obtain a numerical verification of the distribution 
of stress in the rock specimens, measurements of the lateral bulging 
of the nickel-steel jacket were made by means of a very sensitive 
Ewing extensometer for a series of increasing loads. The results 
were obtained for a specimen of Solenhofen limestone in which an 
axial and transverse cavity had been drilled, and the experiments 
carried out in the Engineering Testing Laboratory of McGill Uni- 
versity. 
