Eaton Hodgkinson. 259 



Henry Hodgkinson, rector of Aberfield, Berkshire. He 

 was removed to another school, but instead of showing 

 an inclination to the usual study of languages he seems 

 to have given up everything for mathematics. He was 

 obliged very early to assist his mother in attending to the 

 farm, and at length to leave it, taking all the family 

 into Salford, Manchester, where a business was begun 

 which obtained for him a competency. He continued his 

 mathematical studies and became the leading authority on 

 the strength of materials and the mode of calculating. 

 The labours of a lifetime seemed to culminate in formulae 

 for the purpose, and the most striking instance of their use 

 was in the successful erection of tubular bridges. 



We may be satisfied to quote Mr. Robert Rawson, who 

 knew him well, and who may be trusted as a competent 

 judge to sum up his work.^ 



'The strengths of long pillars of cast iron, wrought 

 iron, cast steel, and Dantzic oak of the same dimensions, 

 are in proportion to the numbers 1,000, 1,745, 2,518, 109. 

 Cast iron is not reduced in strength when its temperature 

 is raised to 600°. 



* The sets in cast iron bearns vary nearly as the square 

 of the force of deflection ; hence any force, however small, 

 will injure the elasticity of cast iron. The strength in tons 

 of beams approaching the best form is measured by the 

 formula, 2\66 ad -^ /, where a — area of section of bottom 

 flange in the middle, d = the depth in inches of the beam, 

 and / = the distance between supports. 



' A general investigation of the position of the neutral 

 line is given on the principle that the forces of extension 

 and compression of a particle vary as a function of its 



' See an account of him in vol. ii. 3rd series, Z?/. and Phil, Soc, Mem. 



s 2 



