652 



THE GREATEST FLYING CREATURE. 



larger the creature the less relative surface and power is needed for 

 its support. 



From the obvious mathematical law that the area in bodies in gen- 

 eral increases as the square of their dimensions, while their weight 

 increased as the cube, it is an apparently plain inference that the Wi- 

 the creature or machine the less the relative area of support may be 

 that l8 , it we consider the mathematical relationship, without reference 

 to the question whether this diminished support is actually physically 

 sufficient or- not), so that we soon reach a condition where we can not 

 imagine flight possible. Thus, if in a soaring- bird which we mav 

 suppose to weigh 2 pounds we should find that it had l square feet of 

 surface or a ratio of a foot to a pound, it would follow from the law 

 just stated that m a soaring- bird of twice the dimension we should 

 have a weight of 16 pounds and an area of 8 square feet, or only half 

 <* square toot of supporting area to the pound of weight, so that if 

 night is possible m the first case it would appear to be highly improb- 

 able in the, second The difficulty grows greater as we^increase the 

 size for when we have a creature of three times the dimensions we 

 shall have twenty-seven times the weight and only nine times the 

 sustaining surface, which is but one-third of a foot to a pound This 

 is a consequence of a mathematical law, from which it would appear 

 to follow that we can not have a Hying creature much greater than a 

 limit of area like the condor, unless endued with extraordinary 

 strength ot wing. 



But this apparently necessary mathematical consequence is not the 

 law of nature, tor while it is found that in the larger bird a smaller 

 area for each pound of the weight is given under the law than in the 

 smaller bird, it is also found (what is another thing) that this smaller 

 area ,s nevertheless sufficient, and that from the mathematical law 

 just cited there does not follow the apparently obvious consequence 

 (notably m the larger creatures like the condor, perhaps less notably 

 in such a creature as the Pterodactyl) that the bird can not be sup- 

 ported, and while the fact is certain that it can, the cause of this does 

 not seem to be clearly known. 



Special cases it may he said, may furnish an exception to what in 

 the nature of things must be the general rule. Such, however, ao-ain 

 does not seem to be the fact. This anomaly which is even now*not 

 generally appreciated seems to have been first noticed by a French 

 observer, M. de Lucy, who about 1868 published a memoir, which I 

 have not seen in the original, but an English translation of which was 

 published in the Fourth Annual Report of the Aeronautical Society 

 of Great Britain for 1869, and an extract from which is here repro- 

 duce^ The same facts are given at greater length in an article by 

 Dr Karl MuHenhoff of Berlin, in the Archly fur die Gesammte 

 Physiologie, Volume XXXV from which Plate V is taken. 



