MEMOIR OF THE LATE PROF. E. HODGKINSON, F.R.S. 157 



greater fidelity and less contortion to meet tlie demands of 

 particular theories. No painstaking or expense was con- 

 sidered too great to make the results of the experiments 

 successful and trustworthy, so that the engineer and phi- 

 losopher alike could place implicit reliance upon them. In 

 these experiments there is recorded_, for the first time_, an 

 element which has furnished a theme for many animated 

 discussions of late years amongst philosophers and practical 

 engineers, and which became an important object of re- 

 search in all Mr. Hodgkinson^s subsequent experiments, 

 viz. set, or the diff'erence between the original position of 

 a strained body and the position which it assumes when 

 the strain is removed. 



This point, which is full of interest and important con- 

 sequences to the practical man, cannot now be discussed. 

 On examination, I believe that I shall be borne out in the 

 statement that, notwithstanding the number of books which 

 have been written during the last thirty years on the 

 strength and strain of materials, some of a more ambitious 

 kind, and others having the humbler object of being use- 

 ful in communicating information to the artisan, still there 

 is none from which a clearer and more satisfactory exposi- 

 tion of this subject can be gathered than from the paper 

 above referred to, by Mr. Hodgkinson in the vol. for 1822. 

 The Tuscan Philosopher, Galileo, has the merit of first 

 propounding a theory of the strength of materials, and ap- 

 plying the unerring principles of geometry to the computa- 

 tion of the strength of beams of given dimensions. With 

 Leibnitz originated the idea of the force of extension of a 

 fibre being proportional to its distance from the lower side 

 of a bent beam. James Bernouilli first suggested the 

 notion (for it never assumed any other shape in his mind) 

 of a neutral line in the section of rupture. But to the late 

 Professor Hodgkinson belonged the merit of giving prac- 

 tical effect, in this paper, to the happy suggestion of Ber- 



