26o Literary and Philosophical Society, 



distance from the neutral line. This includes every hypo- 

 thesis which has been proposed in order to compute the 

 strength of material bodies subjected to strains. 



*When, therefore, Mr. Stephenson was engaged in the 

 novel construction of the Conway and Britannia tubular 

 bridges, he requested the assistance of his friend Mr. 

 Hodgkinson in fixing the best form and dimensions of 

 tubes. The experiments which were devised and carried 

 out by Mr. Hodgkinson with a view to answer the above 

 questions are recorded in the report of the Royal Commis- 

 sioners appointed to inquire into the application of iron to 

 railway structures. 



*Mr. Hodgkinson, by these experiments, sought : — 



* I. To ascertain how far the strain upon a square inch 

 at the top and bottom of the tube would be affected by 

 changing the thickness of the metal, the other dimensions 

 being the same. 



' 2. To obtain the strength of similar tubes. 



' 3. To find the strength of tubes of various forms of 

 section in the middle, and to furnish means of judging of 

 the proper proportions of the metal in the bottom, top, and 

 sides of the tube. 



' 4. To ascertain the relative strength of uniform tubes 

 to bear a weight in all parts of their length ; and whether 

 tubes, tapering in thickness from the middle towards the 

 ends, according to theory, would be equally strong in every 

 part. 



' 5. To obtain the resistance of the tubes, previously 

 tried vertically, to bear a side pressure with an intention to 

 ascertain the effect of the wind upon a tube. 



* 6. To ascertain the strength of small tubes of difTerent 



