336 THE BORDERLAND OF SCIENCE. 



show that the sparrow weighs 339 times less than the 

 Australian crane, but has a relative wing-surface 7 times 

 greater. 



It follows, in fact, from M. de Lucy's experiments 

 that, as we see in nature, birds of similar shape should 

 have wings similarly proportioned, and not wings cor- 

 responding to the relative weight of the birds. The 

 same remark applies to insects ; and we see, in fact, 

 that the bee, the bluebottle, and the common fly in- 

 sects not unlike in their proportions have wings pro- 

 portioned to their surface dimensions ; the same holding 

 amongst long-bodied insects, like the gnat and the 

 dragon-fly, and the same also among the different orders 

 of flying beetles. 



So that, setting apart differences of muscular capacity 

 and adaptation, a man, in order to fly, would need wings 

 bearing the same proportion to his body as we observe 

 in the wings of the sparrow or the pigeon. In fact, the 

 wings commonly assigned to angels by sculptors and 

 painters would not be so disproportioned to the require- 

 ments of flight as has been commonly supposed, if only 

 the muscular power of the human frame were well 

 adapted to act upon wings so placed and shaped, and 

 there were no actual inferiority in the power of human 

 muscles (cross-section for cross-section) as compared 

 with those of birds. 



So far as the practicability of actual flight on man's 

 part is concerned, these two points are, indeed, among the 

 most important we have to consider. It was to Borelli's 

 remarks on these points, in his famous treatise, De 



