42 CHEMICAL MANUEES. 



dry, or dried, which is indispensable, as it contains 5 per cent of 

 moisture. 



Pacific Ocean Isles. — There are a series of coral isles in the 

 Pacific Ocean, in the neighbourhood of the equator, deprived of all 

 vegetation, which have hardly attracted attention. A sample was 

 brought in 1853 to America of a non-nitrogenous guano, collected 

 in one of these islands. Baker Island. Soon afterwards it w^as found 

 that the other isles of the same group were equally rich in guano, 

 viz. Howland, Maiden, Jarvis, Starbuck, Enderbury, and finally 

 the Phoenix Isles, a little further west. As Baker Isle, now for 

 the most part exhausted, yielded the best guano, the typical guano 

 of the isles of the group, a short description of it is now" given. 



Baker Island Guano. — Baker Island is situated at 0"14 of north 

 latitude and 176-22| degrees of longitude west of Greenwich ; 

 1750 metres (say 1 mile) long its w^idth is 1100 metres, and its 

 height above the level of the sea is about 8 metres (26 feet). The 

 chain of coral rocks which surround it, is dry over a surface of 160 

 metres. On this chain is a height of stones, corals and shells, 

 which surround the actual guano deposit. ^ The vegetation of the 

 isle only comprises rare species. The bed of guano is 15 cm. (6 in.) 

 thick on the shore, and 1*60 metres, say b\ feet, in the centre. Its 

 surface is plane, and it occupies a surface of 62-5 hectares, say 156 J 

 acres. The guano isles are the refuge of sea fowl, which come 

 there to make their nests and sit on their eggs. Their excrements^, 

 the food which they bring there (fish and other marine animals), 

 and finally their dead bodies give birth to guano which is, therefore, 

 constantly in course of formation. Looking to its formation, this, 

 guano, like that of Peru, to be described further on, should be very 

 rich in nitrogen, but it is not so. Although rain is generally 

 a rare phenomenon in these tracts, yet the guano is constantly 

 washed by the waves, which are continually broken against the 

 coral chain which fringes the islands. To that has to be added the 

 heat of the day, which is very intense. It follows that the nitrogen- 

 ous matters are rapidly decomposed, producing ammonia and nitric 

 acid ; the first is carried away by the wind, the second is converted 

 into nitrate of soda, which is lost in the depths of the ocean. All 

 the Pacific guanos are met with as a fine pale or dark brown 

 powder according to their percentage of moisture. The brown 

 pow^der is mixed with larger white granules, consisting in great 

 parts of phosphate of ammonia and magnesia.^ According to an 

 analysis of Liebig, Baker guano contains : — 



^ The Pacific Isles are all protected on the sides of the prevailing winds by 

 a chain of coral against which the sea waves are broken up. 



-It follows from researches made since, that the magnesium phosphate in 

 the guano is not tribasic but monacid ; only traces of carbonate of lime were 

 found thei-ein. The composition of the guano is slightly modified since it has 



