for TioenUj Years in succession on the same Land. 335 
of nitrate applied over the two lands was equal to only 71 lbs. 
nitrogen per acre in 1852, and to only 61 lbs. in 1853 and 1854, 
but to 82 lbs. in each year since. 
In the first place it will be observed that, in three of the 
five occasions on which all the other drains ran freely, no result 
is given for the farmyard manure plot. The fact is that, whilst the 
pipe-drains from every one of the other plots in the experimental 
wheat- field rnn freely , perhaps four or five or more times annually, 
the drain from the dunged plot seldom runs at all more than 
once a year, and in some seasons not at all. We must refer to » 
former paper in this Journal * for some further particulars relating 
to this very important result. Stated briefly, it was found that 
the dunged soil, when saturated, retained, within 12 inches from 
the surface, an excess of water which Avould be equivalent to 
about \^ inch of rain more than that held to the same depth on 
the unmanured and the artificially manured plots in the same field. 
The conclusion is obvious, that the dunged soil, with its vast 
accumulation of organic matter, and doubtless greater degree of 
disintegration, porosity, and power of absorption, especially near 
the surface, is enabled to retain much more water. Hence a 
much greater amount and continuity of rain is required to over- 
come its power of retention, and to reach the drains in its case. 
This result is one of very great interest and significance. Thus, 
whether the porosity of a clay soil be increased by the application 
of manure, by mechanical means, or by a combination of the 
two, its power to absorb and retain water, in an available and not 
injurious state, will be proportionately increased ; and, not only 
will the growing crops be thereby rendered more independent of 
drought, but the necessity for artificial drainage will, at any rate 
in some soils, be greatly lessened. 
Not only does the drain-pipe from the dunged plot seldom run, 
but it will be observed that the proportion of nitrogen in its 
drainage water is, in one of the cases given, less than where 82 lbs. 
of nitrogen were supplied as ammonia-salts, and in the other less 
than where 41 lbs, of nitiogen were so supplied. This is the 
case though the dung is estimated to supply to the soil nearly, if 
not quite, 200 lbs. of nitrogen per acre per annum. In connection 
with this point it may be stated that analysis of the soil of the 
dunged plot after 25 years of the application of the manure, 
showed that the top 9 inches contained nearly twice as high a 
percentage of nitrogen as the corresponding layer of any of the 
artificially manured plots. Yet, not once during the 29 years of 
the experiments has the farmyard-manured plot yielded as high a 
total produce (corn and straw together) as one or other of the plots 
manured with mixed mineral manure and ammonia salts or 
* Vol. vii. S.S., Part ]., p. 115. 
