FLIGHT OF INSPXTS. 321 



more than six times stronger than the horse ; and 

 has asserted that if the same proportional strength 

 as is possessed by the Liicamis, or stag-beetle, had 

 been given to the Elephant, that animal would 

 have been capable of tearing up by the roots the 

 largest trees, and of hurling huge rocks against his 

 assailants, like the Giants of ancient mythology. 



But while we must admit that all these facts 

 indicate a remarkable degree of energy in the con- 

 tractile power of the muscular fibres of insects, we 

 should at the same time recollect that the dimi- 

 nutive size of the beings which display those 

 powers is itself the source of a mechanical advan- 

 tage not possessed by larger animals. The efficacy 

 of all mechanical arrangements must ultimately 

 depend on a due proportion between the moving 

 and the resisting forces : hence mechanism of 

 every kind must be adjusted with reference, not 

 merely to the relative, but to the absolute dimen- 

 sions of the structures themselves. This will be 

 evident when we consider that the forces which 

 are called into action are resisted by the cohesion 

 of the particles composing the solid parts of the 

 machine ; and this cohesion, being not a variable, 

 but a constant and definite force, must necessarily 

 limit the dimensions of every mechanical structure, 

 whether iiitended lor stability or for action. An 

 edifice, raised beyond a certain magnitude, will 

 not support itself, because the weight of the mate- 

 rials increases more rapidly than the strength. 

 How often has it been found that a machine, which 

 works admirably in a small model, will totally fail 

 in its performance when constructed on a larger 

 scale. Any lever, of whatever form, may be in- 



VOL. I. Y 



