4 



THE AMERICAN NATURALIST 



[Vol. XL 



evidence, for, as before noted, it consists of a series of witnesses 

 very fairly divided as to whether they can or cannot see the wing- 

 movement, although scientific writers on the sul)ject nearly all 

 follow the latter. We do receive reference to certain parallels, 

 and I shall endeavour to examine these with such lights as I can 

 find. The parallels are, first, the "sailing" or skimming flight 

 of birds (swallows being usually mentioned), and, secondly, 

 parachutes. 



For purposes of comparison in this examination, we will take a 

 typical flying-fish. I have the wings of one, which flew on l)oard 

 a steamer on which J was traveling, before me as I write. Its 

 weight was just over a pound, and it had a wing-area of 62 square 

 inches, very liberally computed. 



Let us consider the bird-flight first. Concerning this we have 

 certain recognized facts to guide us, for which I refer readers to 

 Professor E. J. Marey's work on Animal Mechanism (vol. 2, pp. 

 221-225, 1874). 



We are specially concerned in his acceptance therein of the 

 division of birds into two main classes, viz., those largely given 

 to "sailing" or still-wing flight (which class is found to be endowed 

 with a large wing-surface), and those w^hich confine themselves 

 more to the "rowing" or wing-flapping flight (which, as a class, 

 have short and narrow wings). 



"If," says Professor Marey (loc. cit., p. 221), "we compare 

 together two rowing, or two sailing. . .," arranging as far as possi- 

 ble "to have no difference between them except that of size, we 

 shall find a tolerably constant ratio between the weights of these 

 birds and the surface of their wings." Tables are added of this 

 ratio in various birds, as found by dividing the square root of their 

 wing-surface in s(|uare centimeters by the cube root of their weight 



I will from these tjibies oivc this ratio for tliree of the sailing 

 l)inls and tor three (.f the rowing birds, inelnding the two lowest 

 ratios of tlie latter. I will add on my own account the ratio for 

 the flying-fish, which is (|uite properly comparable with birds in 

 this respect. 



