PHILOSOPHICAL TRANSACTIONS. 
I. The Influence of Stress and Strain on the Action of Physical Forces.* 
By Herbert Tomlinson, B.A. 
Communicated by Professor W. Grylls Adams, ALA., F.R.S. 
Received April 5,—Read April 28, 1881. 
Origin and Purpose of the Investigation. 
More than six years ago, whilst collecting together the results of the most trust¬ 
worthy measurements of the various physical constants, with a view of establishing 
certain relationships which I conceived to exist between them, I was much struck 
with the discrepancies which exist, not only between the observations of different 
experimenters, but also frequently between those of the same individual. Many of 
these discrepancies, no doubt, arise from differences in the purity of the substances 
employed ; but, when all due allowance has been made for such a cause, there still 
exists a large margin, which can only be accounted for by assuming that mere altera¬ 
tion of molecular aggregation must modify always, and in many cases considerably, 
the action of physical forces. This assumption has been already abundantly justified 
by the experimental researches of several eminent philosophers in every part of the 
* In conducting these investigations T have been aided by a grant from the Government Research 
Fund of £4000. For this assistance, which has and will be of the greatest service to me, I here return 
my grateful thanks. I feel myself also under considerable obligations to Sir William Thomson, whose 
valuable paper on “ The Electrodynamic Qualities of Metals ” has really formed the ground-work of 
this memoir. The drawings have for the most part been carefully esecuted by Mr. J. E. Jordan, of the 
Mining Record Office; and for the intelligent carrying out of the various details of the apparatus I am 
indebted to Mr. Kieser, of Elltott Bros., and to Mr. Furse, the Curator of the Physical Museum at 
King’s College, London. 
MDCCCLXXXIH. B 
