Bfl.xic Cinder as Manure. 
137 
sowing the seed, its results might have been better, as it is a 
slow-acting manure. The 4 cwt. of slag contains about GG lb. 
more phosphate than the 3 cwt. of superphosphate, and thus 
leaves an extra amount of residue in the soil for future crops. 
The good effect of farmyard manure in all cases, and of 
nitrate of soda in most cases, and the effect of slag alone as com- 
pared with superphosphate alone, is shown in the table on p. 136. 
On reviewing the whole of the experiments recorded here 
and elsewhere, it seems proved that the finely-divided slag is an 
efficient phosphatic manure on all classes of soils, but is more 
efficacious on heavy clay and on peats, and generally on soils not 
containing: much lime. On calcareous soils it is less certain in 
its effects, and on these superphosphate will always have a 
special value. It is a more slowly-acting manure than super- 
phosphate, and should be applied earlier. In cases where a com- 
paratively slowly-acting manure is wanted, it has advantages 
over superphosphate. Usually, also, it is requisite to apply a 
larger quantity of the slag than of superphosphate to produce 
the same immediate effect, generally about 5 cwt. of slag 
where otherwise 3 cwt. of superphosphate would be used. At 
present prices these amounts of the two several manures cost 
nearly the same. Five or 6 cwt. of slag contains almost double 
as much phosphoric acid as 3 or 4 cwt. of ordinary super- 
phosphate ; and if the effects produced in the first season are the 
same, the dressing of slag leaves a very much larger residue of 
phosphoric acid in the soil, which becomes available, more or less 
slowly, for succeeding crops. Some experiments seem to show 
that the slag residues are more effective than superphosphate 
residues, but more evidence is wanted on this point. 
In purchasing basic cinder, the farmer should obtain, not only 
a guarantee of the percentage of phosphates in the material, but 
a guarantee of the fineness of the powder, such, for example, as 
that 85 per cent, of it will pass through a sieve with 100 meshes 
to the lineal inch — i.e. 10,000 to the square inch — or that 75 
per cent, will pass through a sieve with 120 meshes to the lineal 
inch. There is no immediate prospect of the cinder being 
adulterated with materials that would not be discovered by an 
ordinary analysis, as other phosphates are at the present time 
more expensive ; but Wagner has found that different samples 
of basic cinder, under like conditions, act wilh different degrees 
of rapidity. Thus, some English slags were more efficient than 
most others, and some from Cladno, in Bohemia, acted very 
slowly indeed. This may be due to the different amounts of 
free lime and of decomposable silicates present, but requires more 
investigation. 
