Southwark, Sept. 28, 1851.
226. _Bones of Birds._--Some naturalists speak of the hollowness of the
bones of birds as giving them buoyancy, because they are filled with
air. It strikes me that this reason is inconclusive, for I should
suppose that in the atmosphere, hollow bones, _quite empty_, would be
more buoyant than if filled with air. Perhaps one of your correspondents
will kindly enlighten my ignorance, and explain whether the air with
which the bones are filled is not used by the bird in respiration in the
more rarefied altitudes, and the place supplied by a more gaseous
expiration of less specific gravity than the rarefied atmosphere?
Although of a different class from the queries you usually insert, I
hope you will not think this foreign to the purpose of your useful
miscellany.