Notices respeclhuj New Books. 

 Fiff. 2. 



417 



Fig. 3 represents the 

 manner in which the 

 cells at the top, DE, are 

 constructed. This part 

 of the structure is ana- 

 logous to the rectan- 

 gular cells employed in 

 the construction of the 

 Conway and Menai 

 bridges. In the En- 

 glish invention, thin 

 wrought iron plates are arranged in the form of cells to resist the 

 tendency which such plates have to crumple when subjected to a 

 compressive force ; and in the French invention, comparatively thick 

 bars are arranged in the form of parallelopipeds, to resist the ten- 

 dency which long bars have to bend under a compressive force. 



In mechanical structures generally, it is not surprising that some 

 common principle, in itself scarcely containing the element of no- 

 velty, should be adopted by different persons about the same time. 

 In such cases the merit of invention chiefly consists in the mode in 

 which the parts of the structure are arranged and combined so as to 

 bring the common j)rinciple into a greater or less degree of effi- 

 ciency. Now the principle of cellular structure, taken in connexion 

 with that of the distribution of material for maximum effect, which 

 the French and English inventions have in common with each other, 

 is not in itself new. Mathematicians have long known that the con- 

 dition of maximum strength, in a beam undergoing transverse strain, 



Phil. M(ig. S. I. Vol. ] . No. 5. Maij 1851. 2 F 



