205 



motion ceases.) And so do the feathers with which 

 their bodies are clothed, which increase their bulk, but 

 not their weight in the same proportion. 



The parts of birds chiefly concerned in flying, are 

 the wings and the tail. By the first, the bird sustains 

 and wafts himself along : by the second he is enabled 

 to keep his body steady and upright, particularly in 

 ascending and descending. It is by the largeness and 

 strength of the pectoral muscles that they are qualified 

 for flying. In men these are scarce a seventeenth part 

 of the muscles of the body. In birds they considerably 

 outweigh .-.I! the other muscles together. And this cir- 

 cumstance alone, the want of suitable muscles, makes 

 all human attempts to fly void and vain. 



Nevertheless the art of flying has been seriously at. 

 tempted by many, in various ages, particularly in the 

 time of our famous Friar Bacon, who lived about 500 

 years since, and whom his excellent works shew to 

 have been a rare chymist, an excellent mathematician, 

 a knowing mechanic, and a most accomplished expe- 

 rimental philosopher. Yet even he believed the art 

 of flying possible, and says, he himself knew how to 

 make an engine, in which a man sitting might be able 

 to convey himself through the air like a bird. Nay, he 

 affirms, that there was then another person who had 

 actually tried it with success. 



In flying, f he bird first bends his legs and leaps from 

 the ground ; then opens the joint of his wings so as to 

 make a right line, perpendicular to the sides of his 

 body. Being now raised and strongly vibrating his 

 wings, the air re-acts as much as it is acted upon, and 

 so protrudes his whole body ; but in recovering his 

 wing for fresh strokes, it has a great resistance to 

 overcome. To elude this, the bony .part of the wing, 

 into which the feathers ar^ inserted, moves sideways 

 with its sharp end foremost, and the feathers follow it 

 like a flag. 



All birds have near their tail a little bag, which con. 

 tains oil to moisten their feathers. Geese have two 

 glands for the secretion of this 3 other birds only one* 



