Experimental Crops at Rotliamstcd. 
S)7 
29^ cwts. with mineral manure and ammonia-salts, and to 
5(5]- cwts, with mineral manure and nitrate of soda. Indeed, 
without manure there was not only less produce than in any pre- 
ceding year of the fifteen, but only about one-fourth the average 
amount. With mineral manure and ammonia-salts there was 
again considerably lower produce than in any other of the fifteen 
years with the same manure, and a deficiency of nearly 23 cwts. 
compared with the average. Notwithstanding this, we have the 
remarkable result of 2 tons IG cwts. of hay produced by mineral 
manure and nitrate of soda, or only about 1^ cwt. less than the 
average amount by that manure ; about 2J tons more than with- 
out manure, and 1 V ton more than by the mixture of mineral 
manure and an amount of ammonia-salts containing about the 
same quantity of nitrogen as the nitrate. 
On the assumption that probably about 300 parts of water 
pass through the plants for one part of dry substance fixed, about 
700 tons of water must have been exhaled by the herbage during 
the growth of the 56 cwts. of hay. But, reckoning an inch of 
rain to represent a fall of lOl tons per acre, the 2'79 inches 
which fell in 1870 during April, May, and June, the period of 
active vegetation, could only supply 282 tons of this, provided 
(which would not be the case) none of it was lost by drainage, 
and none of it passed off by evaporation otherwise than through 
the plants themselves. On the same assumptions, the amount 
which fell would be about 160 tons less than sufficient for the 
requirements of the crop grown by mineral manure and ammonia- 
salts, but more than three times as much as would be required 
by the growth of the unmanured produce. 
So strikins: was the difference in the effect of the drought on 
two plots side by side, the one manured with mineral manure 
and a given quantity of nitrogen in the form of ammonia-salts, 
and the other with the same mineral manure and the same 
quantity of nitrogen, but the latter in the form of nitrate of soda 
instead of ammonia-salts, that it was decided, on the removal of 
the crop, to determine the quantities of water existing in the soil 
of the three plots to a depth somewhat greater than the lowest to 
which roots could be traced ; and also to observe the difference 
in the development and distribution of the roots, if any, on the 
different plots. Accordingly, on July 25 and 2C, 1870, samples 
of soil were taken from the three plots to the depth of 54 inches 
in each case, roots having been traced on one of them to within 
a few inches of that depth. 
The plan of collecting and preparing samples of soil for 
analysis will be understood from the following description of the 
process in the present instance : A square yard, comprising a fair 
proportion of the species contributing to the bulk of the herbage, 
VOL. VII.— S. S. H 
