242 Report of Experiments loith different Manures 
as representing with certainty, the exact proportions in which the 
nitrogen of the manured produce has, in point of fact, been 
obtained from the natural and tiie artificial sources respectively. 
These observations will sufficiently indicate the degree of reserva- 
tion with which the figures in the Tables, and the arguments 
founded upon them, should be accepted. 
In regard to the figures in Table VII., which show in lbs. the 
actual i)icrease of nitrogen per acre by its use in man ure, it should be 
explained, that, where 400 lbs. of ammoniacal salts, or 550 lbs. 
of nitrate of soda, were employed per acre, it is estimated that 
82 lbs. of nitrogen were thereby supplied. The 275 lbs. of 
nitrate of soda is, of course, assumed to supply half, and the 
800 lbs. of ammoniacal salts double that amount. The 2000 lbs. 
of sawdust, according to direct analysis, would contain only 
lbs, of nitrogen. It is, then, to these amounts of nitrogen 
supplied, that those recorded in the Table as increase, are to be 
respectively referred. 
But it is in Table VIII., where the increase of nitrogen in the 
produce is, for each experiment, calculated in relation to 100 
parts of it supplied in manure, that the proportion of the nitrogen 
assumed to be recovered, to that supplied, is brought to view the 
most clearly. 
Where ammoniacal salts were used alone (see upper Division 
of Table Vlll.), there was, taking the average of the three years, 
only 27"7 per cent, of the supplied nitrogen recovered in the 
increase. And where the ammoniacal salts and sawdust wpre 
used, there was somewhat less still recovered, namely, 24*5 per 
cent. 
The nitrate of soda, which was employed in one season only, 
and then sown somewhat disadvantageously late, when it was 
used alone, returned in the increase of produce nearly the same 
proportion of its nitrogen as the ammoniacal salts (as just 
quoted) — namely, 23'8 per cent, when the smaller amount, and 
25'8 when the larger amount of the salt was used. But in refer- 
ence to this result, it should be mentioned, that the percciitof/e of 
nitrogen in the hay grown by the nitrate, was notably higher than 
in that grown by the ammoniacal salts in the same season ; in 
fact, the proportion of nitrogen in the former was somewhat 
abnormally high. 
The result was, then, tliat where either ammoniacal salts or 
nitrate of soda were cm})loye(l witliout the aid of the mineral 
manure, there was only about one-fourth of the supplied nitrogen 
recovered in the immediate increase of the hay-crop. 
In connexion with the result just stated, attention m.ay be 
called to the fact, that if, where both mineral and nitrogenous 
manures are employed (see lower Division of Table VIII.), the 
