MANUAL OF AGItlCULTUKE. 277 



"Water, ......... 10'37 



Orc^anic matter and ammoniacal salts, . . . 55'73 



Phosphates, 25-20 



Alkaline salts, 7-50 



Sand, 1-20 



Ammonia contained equal to 18"95. 



This shows a most valuaLle manure, especially rich both in 

 nitrogenous and phosphatic compounds. Phosphatic bodies 

 predominate in many guanos, which are thence called phosphatic 

 guanos. Prom the excessive demand, the supply of Peruvian 

 guano is rapidly becoming exhausted. Xew sources have been 

 made available, but their geographical position being less 

 favourable, the sample of guano yielded is much inferior to the 

 Peruvian. 



Of the artificial manures, various are manufactured with a 

 fixed percentage of nitrogenous and phosphatic compounds. 

 These compounds, however, are for the most part respectively 

 applied in separate com])ositions. As nitrogen food, the princi- 

 pal compounds bestowed upon the soil are the tw^o salts, nitrate 

 of soda and sulphate of ammonia. Besides these there are many 

 available sources of nitrogen supply, including all waste organic 

 substances. The phosphoric acid entering into the composition 

 of artificinl manures is entirely combined with lime, in the form 

 of a salt called phosphate of lime, and its chief sources are 

 animals' bones, coprolites, and apatite. Of these, coprolites are 

 found as concretions in certain rock strata, and are supposed to 

 1)6 the fossilised fieces of gigantic animals, reptiles for the most 

 part existing at the time of the formation of the strata in ques- 

 tion. Apatite is a mineral phosphate of lime, and is found in 

 large quantity in various parts of the world. The 2)hosphate of 

 lime as combined in these cpiarters consists of two molecules of 

 phosphoric acid in chemical union with three atoms of calcium, 

 Ci\.,2V(), — an almost insoluble salt. To overcome the insolu- 

 bility sulphuric acid is added, and it alters the nature of the 

 phosphate, rendering it soluble, by taking from it two atoms of 

 calc'ium — forming with them sulphate of lime or gypsum, and 

 replacing the calcium atoms by their equivalent of hydrogen. 

 Thus, Cag'iPO, -f- 211,80, = 2CaS0, + Cal r,2P0,. This soluble 

 salt is termed super])hoshiite of lime. AVlien bones are treated 

 in this way with sulphuric acid they are known as "dissolved 

 bones;" and in addition to tlu^ ]>hosphate and sulphate of lime, 

 they also possess a considerable (luantity of ammonia, resulting 

 from the organic matter of the bone. When the gradual absorp- 

 tion of i)hos]»lioric acid is desired in the soil, crushed bones and 

 bone "meal" are a])plied, witliout their having received any such 

 dressing. The minute mechanical division of their ]iarticles 

 permits of a ])rolongetl action upon them by the chemical 

 changes occurring in the soil, and an ccpially delayed complete 



