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dressing is required to yield the same result as a smaller quantity 
of the more soluble superphosphate or bonedust. 
Phosphatic Guanos, such as Abrolhos and Sharks Bay guanos, 
contain 44 to 50 per cent. of phosphate and only one half per cent. 
of ammonia, the balance being mostly sand and moisture. They can 
be got in several ton lots at a very reasonable price, and answer 
well when mixed with a small proportion of a more soluble phos- 
phate, such as concentrated superphosphate and sulphate of am. 
monia. A fair dressing would be 3 to 4 ewt. to the acre. 
The Cave Bat Guano found on our coastal limestone hills is 
also a phosphatic manure, and contains 1 to 3-5 per cent. of 
ammonia and 12 to 15 per cent. phosphate of lime readily available. 
Thomas’ Phosphate Powder, or Basic Slag, is another source of 
phosphates. It is derived by means of the Thomas Gilchrist process 
in making steel from pig iron by smelting it in converters lined with 
lime; when the iron is melted the air is blown through, part of the 
iron and impurities are oxidised, and the phosphoric acid combines 
with the lime, forming phosphate of lime. This contains 14 to 17 
per cent. of phosphoric acid, equal to 30 to 36 per cent. of phos- 
phate of lime, and also 40 per cent. lime, and 18 per cent. iron 
oxides, and 6 per cent. sand. It is very cheap in England, where it 
used to sell at the factories for £1 a ton, and was retailed at 30s., 
but is now much dearer. It is so finely divided that it acts very 
readily. 
The soils most suitable for Basic Slag are: lands of a peaty 
character, rich in organic matter. Its action on heavy stiff clay is 
very beneficial, as it helps to disintegrate the soil and make it more 
friable, at the same time liberating a proportion of the natural 
potash in which most clay soils abound. Also on all kinds of pas- 
ture land, and on. poor hill pastures. On light soils the addition of 
potash is usually necessary. On soils subject to “finger and toe” and 
“ouff-ball” it should be given the preference for roots. It must not 
be mixed with sulphate of ammonia, guano, or dried blood. 
Coprolites and Apatites constitute mineral phosphates of great 
value, either ground into a fine powder or for making superphos- 
phates; they occur in some geological formations under the form 
of concretions, and consist of the fossil exerements and remains of 
extinct animals. They vary in richness from 10 to 75 per cent. of 
phosphates. 
Superphosphate of Lime.—Hither of the raw materials referred 
to already are ground and treated with sulphuric acid, thereby made 
more soluble, and hence quicker, in its action. The actual composi- 
tion of superphosphate varies with the material of which it is made, 
and ranges from 35 to 40 per cent. down to 20 per cent. phosphates 
rendered soluble. In this state, owing to its diffusibility, superphos- 
phate is able to permeate through a greater quantity of soil, and 
penetrates further than other merely mechanically-divided phos- 
