146 MARVELS OF THE ANIMAL WORLD 



which, under the influence of air and light, under- 

 goes a transformation of colour and changes to 

 various shades of blue, green, and yellow. In 

 former days it was used as a dye. 



The bones of animals, besides yielding a weak 

 form of glue, are also used in the production of 

 charcoal which, when pulverised into a fine powder, 

 is known commercially as bone-black and is largely 

 utiUsed in the manufacture of printer's-ink, boot- 

 blacking, and for decolorising syrups. The in- 

 habitants of the Pacific Isles convert the wing-bones 

 of the albatross into tobacco pipes ; and Fitz- 

 stephen, in his History of London, tells us that it 

 was customary in the twelfth century for the young 

 men to fasten the leg-bones of animals under their 

 feet by means of thongs, and then sHde over the 

 ice by pushing themselves along with iron-shod 

 poles. Ammonia is a product which is sometimes 

 prepared from bones and horns ; and albumen 

 or the white of egg is a useful commodity used in 

 photography, in the industry of caUco printing, 

 and for sugar refining. 



As a fertiliser of land, the substance known as 

 guano (the accumulated and decomposed droppings 

 that sea-birds, such as gulls, cormorants, and 

 penguins deposit on many islands in the Pacific 

 Ocean, and also that of the bats which inhabit 

 the caves of the Southern States of South America) 

 is very valuable to the agriculturist ; while the 

 rotted bodies of fish, as well as the ground -up shells 

 of oysters, are other forms of manure which are 

 highly beneficial when used as a dressing for the soil. 



