70 MANUAL FOR SUGAR GROWERS. 



as guanos ; tliese for the most part consist of the 

 excrement of various birds. Guanos vary in com- 

 position according to the length of time they have 

 been deposited, fresh guano closely resembling 

 farm-yard manure in its general character, except 

 that it is extremely concentrated from the absence 

 of litter ; hence, guano of this type is a general 

 manure, supplying nitrogen, phosphate, and a small 

 quantity of potash. In the older guanos the am- 

 monia has largely disajDpeared, so that these gua- 

 nos are essentially phosphatic in their nature. Ni- 

 trogenous or ammoniacal guanos are becoming less 

 and less abundant, so that much of the manure sold 

 under the name of guano is a manure artificially 

 compounded, usually being of excellent quality and 

 preferable to raw guano. 



There is one form of phosphatic manure which, 

 so far, has received but little attention from West 

 Indian planters, — basic slag, basic phosphate, or 

 Thomas phosphate, as it is variously termed. In 

 the manufacture of steel from cast iron some difii- 

 culty was experienced, owdng to the presence of 

 phosphorus in the iron. It is found possible to re- 

 move this by the use of lime, from Avhich results the 

 basic slag, a substance containing the phosphorus 

 in combination with the lime as basic phosphate of 

 lime. This substance contains from fifteen to 

 twenty per cent, of phosphoric acid, equal to about 

 thirty-four to forty-five per cent, of tri-calcium phos- 

 phate ; hence, it is more concentrated than super- 

 phosphate. It is not an acid manure, as super- 

 phosphate is, and on soils deficient in lime, as so 



