BIRDS SELDOM BURIED. 253 



its tusks or any portion of its skeleton found. The natives 

 declare that the herd bury their deceased companions if 

 these die before reaching the solitary valley to which they 

 are supposed to withdraw on feeling the approach of death. 

 Every one believes in the existence of this valley, though 

 it is mysteriously concealed from human eyes, and Sindbad 

 recognised it at once, when, on recovering his senses after 

 his alarming journey, he "found, himself among the bones 

 of elephants, and knew that this was their burial-place." 



Birds, having no such burial-places, and being less 

 liable to be buried alive than other animals, are less fre- 

 quently found fossilised. But when flying near volcanoes 

 in a state of eruption, they have often been observed to 

 drop down, killed by the noxious vapours, and if buried in 

 fine volcanic ashes not only their bones, but the form 

 of their bodies, would be preserved. Moreover, they 

 sometimes fall into lakes when chased by hawks, and 

 those which build near water are sometimes surprised 

 and swept away by a flood, and in these cases, if they do 

 not float long enough to be devoured, which, being very 

 light, they probably do, they may chance to sink, and 

 be buried in mud. 



The chief remains of ancient birds are those of the 

 large wingless kinds, whose bones were filled with marrow, 

 instead of air, which made their bodies considerably heavier, 

 and more likely to sink, while their want of wings put 

 them on a level with other animals. 



The most extensive accumulations of organic matter 

 due to birds are, however, the great guano beds of Peru, 

 Bolivia, Africa, &c. Three-fifths of the guano is soluble, 



