466 Abstract Report of Agricultural Discussions. 
Tlio value, then, both of giiano and superphosphate depends on 
their concentrated form. 
If sewage had been compared with bulky farm-yard manure, 
instead of with guano, "very different would have been the results. 
To illustrate this, let me point out the composition of fresh and of 
rotten farm-yard manure. Without entering into minutiae, I may 
state that a ton of rotten dung contains 8^ lbs. of soluble phosjjhate 
of lime. This, at the usual price taken by chemists, is worth 2s. 
Then it contains 10 lbs. of potash, worth 2s. 6d. ; 16 lbs. of ammonia, 
worth 8s. ; and 12^ lbs. of insoluble phosphate, worth Is. ; thus we 
arrive at los. 6d. as the calculated valne oi a ton of farm-yard manure. 
I need not say that this calculated value is far above that which we 
actually pay. 3s. per ton, or at the most 5s. per ton, is, I believe, 
the price generally given for farm-yard manure. Making the same 
calculations for fresh faiTU-yard manure, I find the following result. 
We have 6^ lbs. of soluble phosphate of lime, worth Is. 8c?. ; 8^ lbs. 
of insoluble phosphate of lime, 8^fZ. ; 12jlbs. of potash, 3s. l^d.; 
and 15 lbs. of ammonia, 7s. 6d. ; or a total of 13s. We thus get 
a value for rotten manure of Gd. less per ton than for fresh ; and 
in both cases assume the value of faim-yard manure to be two or 
three times as high as it is in reality. Now, in dealing with a 
manure still more bulky, still less under our control than farm-yard 
manure, I cannot see why we are not to take into consideration 
that its value in a great measure depends on its being manageable. 
Sewage manure, then, is only valuable in special cases, such as 
that of land that has in itself little or no fertilising matter, but is 
porous, and allows certain crops to penetrate deep in search of food 
— that is to say, a sandy soil, such as those analysed in the follow- 
ing Table : — 
Akalyses of Four Sandy Soils. 
I. 
II. 
III. 
IV. 
Silica and quartz sand 
96-000 
92-014 
90-221 
94-70 
•500 
2-652 
2-106 
1-60 
2-000 
3-192 
3-951 
2*00 
trace 
-480 
•960 
-001 
•243 
-539 
1-10 
trace 
•700 
•730 
trace 
> > 
•125 
-066 
> ) 
•026 
•010 
} 
-078 
-367 
trace 
trace 
trace 
•01 
Organic matter (humus) . . 
1-499 
•490 
1-04 
•50 
100-000 
100-000 
100-000 
100-00 
You will notice that the preponderating element in these sandy soils 
is silica. In some of them there is hardly any potash and phosphoric 
acid, and in two only a small quantity of phosphoric acid. These 
soils, then, are greatly deficient in every description of food. 
