for Ttventi/ Years in succession on the same Land. 
341 
hut not heavy rains (or snow-falls), but at tlie latter date about 
two-thirds of an inch of melted snow and rain were registered, 
all the drains ran, and samples were collected and sent to 
Dr. Frankland. After such an unusual washing out of the soil 
since the sowing of the manures in October, the drainage of 
February 2Gth is seen to contain, for that period of the year, a 
very small amount of nitrogen as nitrates and nitrites. There 
is still something like gradation according to the amount of 
nitrogen supplied in the manure ; and, as would be expected, 
there is less in the drainage from the nitrated plot than in that 
from Plot 7, which receives the same amount of nitrogen annually, 
but applied as ammonia-salts in the autumn. 
In connection with the very unusually large amount of water 
passing from the land by drainage during the past winter, 
1872—73, it is of much interest to remark that, whilst at the 
present time (June 1873) the plots in the experimental wheat- 
field which received their dressing of ammonia-salts in October, 
are looking very much worse than usual, in fact, extremely 
unpromising, others, which were top-dressed with ammonia-salts 
or nitrate of soda in March, show much greater luxuriance. 
With regard to the dunged plot (2), it has been explained 
(p. 335), that, owing to the greatly increased porosity of the soil 
by the application of farmyard manure so many years in suc- 
cession, the drains from it very seldom run. It happens, there- 
fore, that they do so only when there is a very great excess of 
rain ; and, when there is such excess, a surface-drain, which first 
crosses the furrows of all the other plots, then crossed that of the 
dung, and passed not many yards from the outfall of that plot, 
has generally been running, so that there has sometimes been 
doubt whether the drainage from the dunged plot were not more 
or less affected by the percolation of this surface-water. Other 
cross-surface drains have, however, from time to time, been cut, 
to obviate this as far as possible ; and it is believed that, at any 
rate during the past winter, there has been no danger of such 
percolation. Moreover, the results relating to Plot 2, recorded 
in the Table, though so different at the four periods of collection, 
are so far consistent with each other that, in each case, the 
drainage-water contains somewhat less nitrogen as nitrates and 
nitrites than that collected at the corresponding date from Plot 6, 
which received only 41 lbs. of nitrogen per acre per annum, but 
in the form of ammonia-salts; whilst, as already stated (p. 335), 
the dung is estimated to supply nearly, if not quite, 200 lbs. 
of nitrogen per acre per annum. But there has been a great 
accumulation of the nitrogen supplied by manure in the soil of 
the dunged plot, especially near the surface, and very much 
more than in that of the plots manured with ammonia-salts or 
2 A 2 
