50 
Bulletin 65. 
The results indicate an increase in the humus present, but the 
analyses do not show conclusively that this was due to the applica¬ 
tion of manure, though the indications are that it had a perceptible 
effect. The results in regard to the phosphoric acid are difficult to 
bring into harmony with the facts as recorded or with one another, 
but the general results are in the same direction as those obtained 
from the samples taken in the autumn of 1897, namely, an increase. 
The increase in the nitrogen is not very pronounced, but seemingly 
quite general. The most marked result, however, recorded in the 
last table is the increased extent to which the phosphoric acid pres¬ 
ent in the soil can be extracted with the ammoniacal solution 
of the humus. It is entirely out of the question to attribute 
this large percentage of the phosphoric acid found in the humus so¬ 
lution to any turbidity which, owing to the dark color of the 
solution, might have passed through the filter and escaped detection. 
I regret that I did not examine the hydrochloric acid with which 
the soil was washed to determine how much phosphoric acid was 
removed by it. An inspection of the table shows that from 14 to 
60 per cent, of the total soluble phosphoric acid was found in the 
ammoniacal humus solution. 
§ 104. If we recall the amount of nitrogen found in the pre¬ 
cipitated humus, about 5.5 per cent., we will see that the observa¬ 
tion made on the phosphoric acid is also applicable to the nitrogen, 
only in a different degree. The humus contained from 14 to 60 
per cent, of the former, but 40 or more per cent, of the latter. 
The manure which was applied to this soil was analyzed, the 
results, together with some observations on its effects, etc., are given 
in Bulletin 58, pp. 13, 18, 36, et seq. 
The sulfuric acid was determined in the samples taken in 
1899, giving for No. 3, manured and not manured, 1.320 per cent, 
and 0.350 per cent.; for No 2, 0.333 and 0.633 per cent.; for No. 1, 
0.683 and 0.314 per cent. If we compute this into sodic sulfate, as 
we have done elsewhere, it will be seen that the sulfates have either 
been removed or carried down into the soil beyond the reach of our 
sample, and either is an improvement. 
§ 105. The results of this experiment are readily recognizable 
in the improved condition of the soil. The figures given as repre¬ 
senting the composition of the samples taken in the autumn of 
1899, may be right or wrong, but the improvement in the soil is 
much more pronounced than any analytical results can indicate, 
and after all of our seeking after facts and explanations, we are fully 
satisfied that there is much in the aggregate effect, whether it has 
been produced by moisture, aeration, frost or sunshine, that has es¬ 
caped our analysis, and while it is perfectly patent, it is not subject 
to clear and definite formulation. The application of manure pro- 
