322 
Tice Trials of Ploughs at P^arwich. 
made upon the plougli, yet it is impossible to entirely eliminate 
the man, and the competitor ought to be sufficiently alive to 
his own interests to take care that they are not allowed to 
suffer in the hands of an unskilful workman. 
The measure of the efficiency of the ploughs has, as on 
former occasions, been taken as the ratio between the draught 
in pounds and the weight of earth moved in a given distance. 
The first record is given by the dynamometer. To obtain the 
second of these a square yard of earth was removed to the depth 
ploughed, and weighed, and the results are tabulated in column 
9 of the tables on the opposite page. The comparison between 
draught and weight of earth moved only holds good in trials made 
on similar land and under the same conditions, as it frequently 
happens that land which weighs less per cubic foot offers, from 
its more plastic nature, greater resistance to ploughing than land 
which is actually heavier in weight, but which, from its more 
friable nature, is less resistant. This is borne out by the com- 
parison in the present instance of the trials in the Light and 
Heavy Land Classes.' This, together with different conditions 
of weather, must not be lost sight of in any comparison which 
is attempted with other records. 
Through having all the trials of the Light Land Classes made 
in the one field and on such very similar plots, a useful com- 
parison can be drawn between them, which could not have been 
done had they been tried on the various plots in the fields in 
which the earlier trials were made. In Classes I. and III. these 
trials took place in the old ley, to ojien up which would doubt- 
less take more draught than the breaking up of similar land in 
stubble. The results obtained, however, Avould be in no way 
comparable with those obtained in Classes IV., V., and VI., 
which were tried in another field, or with those of Class VIII., 
tried in a third field. 
For the Heavy Land Classes the dynamometer trials ■were 
made in the lower part of the same field as the earlier trials in 
such classes, the most level piece of the field being selected for 
such purpose ; the land was somewhat lighter here than at the 
upper end of the field. These trials were conducted in precisely 
the same manner as already described in the Light Land Classes. 
An interesting comparison may be made between the single, 
double, and three- furrow ploughs of any one maker. In such 
case the weight of ploughs does not increase in the same propor- 
tion as the weight of earth which they are capable of moving ; 
* The weight per cubic foot of each, reduced from the weights given in 
column 8 of tlie tables, is practically identical, though the difference in 
the nature of the land was quite evident. 
