368 
Steam Engine. 
ness of a second Hotsc, equal in point of strength to the 
former. Then if the two horses, thus attached to the 
ears E and F, be made to pass over the walk in the same 
direction, following each other constantly at the distance 
of a semi-circumference : while that which draws at the 
ear E overcomes the whole pressure and resistance op- 
posed by the work, the other which draws at F by the 
cord over the pulley />, will raise the weight w of the steel- 
yard ; which therefore, by being moved to and fro upon 
the arm f i, may be brought to exhibit an exact counter- 
poise, or measure of the exertion and power of the horse. 
And in order to ensure the greatest degree of accuracy in 
this respect, the motion of the two animals, and the po- 
sition of the weight w, should be so adjusted, that the 
same weight should be shewn by the graduations both of 
the spring and of the lever steelyard. The shaking of the 
machinery will in some measure disturb the effect ; but 
an ingenious manager of the experiments will find means 
of checking this : and as to the centrifugal force to which 
the weight w is exposed, it will never be of any material 
consequence in any of the slow motions which will be pro- 
duced by this kind of work. 
Each experiment should occupy the space of a fair day^s 
w^ork for the horses : for the conclusions deduced from 
shorter and irregular effo' ts are always erroneous in ex- 
cess, and should be guarded against. The rate at which 
the animals move may readily be ascertained from the 
known circumference of the walk, and the number of 
rounds they are observed to make in 10 or 15 minutes^ 
Thus, by continuing the experiments day after day, va- 
rying the velocity of the motion in some cases, and the ra- 
dius of walk in others, such a series of results might at 
length be obtained, as would in a great measure remove 
the obscurity and doubt in which this business is at pre» 
sent enveloped. It is scarcely necessary to suggest the 
