320 
The Trials of Flo'tojhs at War wide. 
to a dial-counter which registers the number of revolutions. 
When there is no pull on the draw-bar the small wheel is in 
contact with the centre of the disc, and consequently there is no 
motion, but so soon as any load comes on the bar the small 
wheel is pulled out from the centre, approaching more nearly 
to the periphery of the I’evolving disc as the load increases, and 
as it does so the speed of its rotation increases ; in this way 
a numerical representation of the draught is given by the 
counter. 
In order to take up any undue sudden strain which might 
come upon the springs from the plough fouling a large stone or 
root of a tree, the forward end of the draw-bar has a piston 
fitted on it working in an oil cylinder. 
To give actual values to these representations of draught it 
is necessary to calibrate the instrument. For this purpose it 
is suspended vertically and weights are hung from the draw- 
bar, and the driving wheel is rotated so that it shall repre- 
sent a given travel — say, one hundred yards. A diagram is 
recorded and the reading of the counter is taken. By repeating 
such tests with increasing loads, co-efficients are arrived at 
which, used as multipliers for the measurements of the diagram, 
and the numerical reading of the counter, give the actual draught 
in pounds at any time. This operation was gone through not 
only befoi’e the trials, but Avas repeated on tlie trial-ground 
immediately afterwards with the dynamometer under exactly 
the same conditions as those under Avhich it had been working, 
and from the co-efficients thus arrived at the figures representing 
the amount of draught in the tables Avere calculated. 
With the view of making the draught as uniform as possible 
for all the competitors, and of eliminating errors arising from 
irregular draught which would to some extent occur in draAving 
the ploughs with different teams of horses, it was arranged to 
haul the dynamometer to which the ploughs Avere attached by 
means of steam ploughing tackle, for which purpose a double 
set of Fowler’s steam ploughing engines was provided. An 
engine was placed at each headland, and Avhile one engine was 
hauling the dynamometer up the field, the rope of the other 
engine was being paid out and led by a man and horse to the 
upper end of the field ready for the next run down the field. 
Obviously in this arrangement there Avas a little difficulty in 
turning at each headland, the plough and dynamometer having 
to be hauled round by hand ; but Avith many Avilling helpers 
this difficulty was reduced to a minimum, while the advantages 
of the more uniform pull, and the facility of regulating the 
engines’ speed in comparative tri,als such as these, completely 
