CHAP. XIX. SUSPENSION-CHAINS PROPOSED. 427 



were of the most elaborate and eventually conclusive 

 character, bringing to light many new and important 

 facts of great practical value. The due proportions and 

 thicknesses of the top, bottom, and sides of the tubes 

 were arrived at after a vast number of separate trials ; 

 one of the results of the experiments being the adoption 

 < >f Mr. Fairbairn's invention of rectangular hollow cells 

 in the top of the beam for the purpose of giving it the 

 requisite degree of strength. About the end of August 

 it was thought desirable to obtain the assistance of a 

 mathematician, who should prepare a formula by which 

 the strength of a full-sized tube might be calculated 

 from the results of the experiments made with tubes of 

 smaller dimensions. Professor Hodgkinson was accord- 

 ingly called in, and he proceeded to verify and confirm the 

 experiments which Mr. Fairbairn had made, and after- 

 wards reduced them to the required formulae ; though 

 Mr. Fairbairn states that they did not appear in time to 

 be of any practical service in proportioning the parts of 

 the largest tubes. 1 



Mr. Stephenson's time was so much engrossed with 

 his extensive engineering business that he was in a 

 great measure precluded from devoting himself to the 

 consideration of the practical details, which he felt 

 were safe in the hands of Mr. Fairbairn "a gentle- 

 man," as he stated to the committee of the Com- 

 mons, " whose experience was greater than that of any 

 other man in England." The results of the experi- 

 ments were communicated to him from time to time, 

 and were regarded by him as exceedingly satisfactory. 

 It would appear, however, that while Mr. Fairbairn 

 urged the sufficient rigidity and strength of the tubes 

 without the aid of chains, Mr. Stephenson had not quite 

 made up his mind upon the point. Mr. Hodgkinson, also, 



Fairbairn's ' Account,' p. 22. 



