31G Report of Experiments on the Growth of Barlci/, 
since there is evidence tliat the excessive supply of ammonia- 
salts during the first six years left a residue of nitrogen which 
was effective for ten, if not more, years afterwards, not only do 
the figures for the first six years understate the total or final 
effect of the ammonia applied during that period, but those for 
the subsequent years overstate the result for those years. The 
average columns of the Table give, however, not the mere 
arithmetical means of the results for the individual years, but 
the direct averages for the periods ; and the result over the 
twenty years is, that, instead of only 2*13 lbs. of ammonia 
required when superphosphate and only 200 lbs. of ammonia- 
salts were used, there were 2*49 lbs. required when, for the first 
6 of the 20 years, 400 lbs., for the next 10 years 200 lbs., ammo- 
nia-salts, and for the last 4 years 275 lbs. nitrate of soda, were 
applied. . There is also a considerably less favourable result 
without than with the superphosphate. Lastly, as in the experi- 
ments with the smaller quantity of ammonia-salts every year, 
the variation of result according to season is very considerable ; 
but, owing to the excess of ammonia applied in the early years, 
and to the effects of the accumulation afterwards, the exact figures 
for the individual years cannot be taken in illustration of the point. 
During the last eight years of the twenty, one-half of the plots 
of Series II. received, besides the same manures as the other half, 
400 lbs. of silicate of soda, per acre, per annum. The four 
portions so treated are respectively designated 1 AAS, 2 AAS, 
&c. ; and the results are recorded in the Table under the head- 
ing of Series III. Almost every year it was quite obvious to the 
eye that there was a marked effect from the silicate on Plots 1 
and 3, that is where no superphosphate was used ; but compara- 
tively little, if any, on Plots 2 and 4 with superphosphate. So 
striking was this result, that the silicate was examined in the 
laboratory to ascertain whether it contained any phosphate. It 
was found not to contain any ; nor did it contain nitrate or 
nitrogen in any other form. Perhaps the most proba!)le sup- 
position is, that by the action of the alkaline silicate on the soil, 
otherwise locked up phosphoric acid was rendered available for 
the plants. It is possible, however, that, when the superphos- 
phate was used, a secondary result of its action within the soil 
was the liberation of silicates, which, without it, were not avail- 
able in sufficient quantity ; and hence the little effect of the 
direct supply of silicates where the superphosphate was used, and 
the marked effect where it was not employed. Or, is it that 
when the acid-phosphate and alkaline silicate are mixed together, 
they are rendered comparatively insoluble and inactive? The 
result may perhaps be due in part to more than one of these actions. 
Whatever may be the explanation of the fact, the Table shows 
