1909 - 10 .] Method of investigating Certain Systems of Stress. 45 
For the Hele-Shaw apparatus, without which these experiments could 
not have been carried out, the author is indebted to the Carnegie Trustees. 
REFERENCES. 
(1) Brit. Assoc. Report, 1898, p. 136. (2) Ibid., p. 143. 
(3) Proc. Inst. Mech. Eng., 1905, p. 141. 
{Issued separately December 23 , 1909 . 
