upon Dect-root. 
531 
V. Artijicial Manures alone. 
Tons. 
"7 cwt. rape 20j 
14 bushels bones ..... 20 
3 cwt. guano 20^ 
7 cwt. rags, (estimated) about ... 20 
The agreement, by actual wcisliing, between the three first arti- 
ficial manures is very close. The effect of all is but weak, and 
the increase of crop would barely pay for their use, being only 5 
tons, worth about bOs. to consume on the land. 
The third class evidently marks itself out as follows : — 
Artificial Manure. Tons. 
13 loads dung 27^ 
13 loads dung . . 1 cwt. rape-dust . 27 
1^ loads dung . .14 bushels bones . 26 
26 loads dung 28^ 
These amounts again may be taken as practically the same. No 
advantage is gained by exceeding the single dressing of dung. It 
seems a confirmation of the inference that there is a limit to the 
profitable use of dung, to find that bones and rape-dust, each 
efficient when used alone, fail equally with the additional dose of 
dung in raising the produce above the standard amount, in which 
there certainly is a striking agreement between the four lots. In 
the second class, then, the artificial manures gave each about 5 
tons additional produce per acre. In the third class, the single 
dressing of dung gives about 12 tons, which is not increased by 
the further use of bones, rape, or sensibly even by doubling the 
dung. 
The remaining class shows a different result : — 
1 3 loads of dung 7 cwt. rags 36 tons 
13 lorids of dung 3 cwt. guano 36 tons 
Here we obtain a very large increase by adding two different 
artificial manures separately to the full dose of dung. The 
question arises, why these two manures should act so much 
better ; a question I am unable to answer. But in the inte- 
resting work on ' Rurnl Economy,' which Boussingault has 
lateh* published, and Mr. Law has translated, there is a very 
copious table in which the value of manures is stated according to 
the quantity of azote which they contain. In that table the 
manures we are now dealing Avith stand thus : — 
Azote. 
Rape-dust ...... 5J 
Bones ....... 6y 
Best guano . . . . . . 15f 
Woollen rags . , . . . . 20j 
