158 
Oh tlie Comparative Value of 
" 4. A crop with so early a tendency to form bulbs that it 
affords us the means, by sowing early, of getting an 
early crop for autumnal feeding ; or, by sowing late, of 
securing a crop when no other known means could 
effect it, and when our land, owing to peculiar cir- 
cumstances, has not been fit for the seed at an earlier 
period." 
" The fertilising influence of the bones will be quadrupled. 
The various circumstances under which the several applications 
which support this conclusion were tried, without one contradic- 
tor)/ result, place that conclusion beyond the possibility of error, 
and justify us in asserting that practice has realised what theory 
previously promised in the most important saving which has 
ever been held out in the use of manure.*' 
The experience of fai-mers in all parts of the world has since 
fully confirmed the correctness of Mr. Hannam's conclusions, 
and it appears to me both an irrational and a retrograde step if 
agriculturists were to attempt the use of raw phosphatic mine- 
rals instead of applying them treated with acid. 
Briefly stated, the following are my views on the compara- 
tive efficacy of different kinds of phosphatic materials and the 
economy of applying them to the land, either in a raw state or 
after treatment with acid : — 
1. Acid or soluble phosphate is not usefully taken up as 
such by plants, and has to become insoluble in the 
soil before it can become plant-food. 
2. The efficacy of insoluble phosphate of lime as a fer- 
tilising ingredient rises or falls with the more or less 
finely divided state in which it occurs in various 
phosphatic materials. 
3. The finer the state of division of the particles of phos- 
phate of lime in phosphatic materials the more readily 
it is soluble in water, and the more efficacious are the 
phosphatic materials as manure. Therefore coarsely 
ground coprolites and other phosphatic minerals are 
less soluble and less efficacious than in a state of fine 
powder. 
4. In porous soft bones the phosphate of lime occurs in 
a different state of aggregation than in hard bones, 
and in the former condition phosphate is more soluble 
and efficacious than in the latter, and for the same 
reason the phosphate of lime in fine bone-dust is more 
soluble in water and more efficacious than the phos- 
phate of lime in J-inch bones or coarse bone-dust. 
5. In the form of hard crystalline phosphate of lime, 
