34 THE BONES. 



spawn, worms, or other soft water insects. One other beak 

 only shall be mentioned, namely, that of the Spoonbill, 

 which, in its food, partaking of the nature of the Heron 

 and Duck tribes, is provided accordingly ; its interior part 

 being furnished with rough projections which prevent the 

 escape of such slippery things as small fish, while its wide 

 spoon-shaped end enables it to crush and sift mud and 

 weeds for worms or soft vegetable matter. 



The bones of birds, like those of animals, are for the 

 most part white, but in other respects, they differ materially 

 from those of four-footed animals, being composed of a thin, 

 firm, and partly elastic substance, formed in layers ap- 

 parently fastened together, and almost always hollow ; the 

 cavities never containing marrow, but air, and communi- 

 cating with the lungs by considerable openings ; whereby 

 they are rendered buoyant and light to a much greater 

 degree than is generally supposed. Thus a portion of the 

 leg of a Goose, about two inches in length, weighed about 

 forty grains, while a piece of the leg of a rabbit (the marrow 

 having been extracted, and both being perfectly dry, and as 

 nearly as possible of the same thickness and length,) weighed 

 seventy-five grains, or nearly twice the weight of the 

 similarly-sized bone of the Goose ; and yet so firm and strong 

 was this latter, that although in diameter it was less than 

 one-eighth of an inch, and the solid tubular part not more 

 than one -hundredth part of an inch in thickness, it could not 

 be broken asunder by the hand. 



It is upon this principle mechanics and engineers act 

 in constructing strong supports, knowing that if any quan- 

 tity of material is to be fabricated -into a rod of a certain 

 length, the rod will be strong in proportion to its thickness ; 

 and that if the figure remains the same, that thickness 

 can only be increased by making it hollow. Therefore, 

 hollow rods or tubes of the same length and quantity of 

 matter have more strength than solid ones of less dia- 

 meter. This is but one out of the hundreds of instances 

 in which the wisdom of man has been perfected by studying 

 the mode by which the great Creator accomplishes hia 

 purposes. 



