when treating on the loco-motive engine, enlarge a little more upon the effect of this, in diminishing the performance of these kind of engines.

III. HORSES.

The power of a horse, or that part of his muscular exertion, which, in travelling, he is capable of applying upon the load, has been variously stated by different authors. It is not the force he is capable of exerting at a dead pull, or for a short period, by which we are to judge of, or estimate, his strength; it is what he can exert daily, and day after day for a long period, without injury to his physical powers, that we are to take as the criterion for practice.

A Rail-road is peculiarly adapted to show the power of a horse, as he is continually employed in overcoming the same resistance, and the inclination of the road in general has little effect upon the power required to overcome the gravity of his own weight.

The following Tables will show different Rail-roads, where horses have been used for some years, and the respective resistances which the inclination of the road and the friction of the carriages presented to the action of the horse.

TABLE III.

Table of the line of road on which one horse travels with six loaded carriages, each weighing 8,540lbs. similar to Experiment IV. No. 1.; and returns with six empty carriages, each weighing 2,604lbs. same as Experiment IV. No. 7.-Edge-rail, Killingworth Colliery Rail-road, friction loaded carriages 40lbs., empty carriages 14lbs.

On examining the above Table, it will be seen that the average resistance with the load is about 60 lbs. ; and in returning with the empty carriages 157 lbs., the mean 109 lbs. -The distance 2156 yards.

The horses were very large and heavy; they

.

generally traversed that distance eight times a day, being in all about nineteen miles.-There were four horses regularly employed, but it was found necessary to keep a spare horse, to give the others alternately a day's rest; so that, in fact, five horses were kept to perform the constant work of four horses effectively.

TABLE IV.

Table of the performance of horses upon the Backworth Colliery Edge-rail-road, where a horse takes six loaded carriages, each weighing 9,010lbs. down the plane, and returns with six empty carriages up the plane, each weighing 3,080lbs. Friction of loaded carriages 42lbs. and of empty 15lbs.

The preceding Table will show the performance of the horses upon a portion of the Backworth Colliery Rail-road; these horses, like those employed on the Killingworth Rail-road, are extremely powerful, as may be presumed. The average resistance with the loaded carriages is 42 lbs., and with the empty carriages 189 lbs., giving a mean of 115 lbs.; they traverse the distance backwards and forwards most frequently eight times a day, making nineteen miles. This Table may be taken as the maximum performance of horses, and will shew the resistance which a very powerful horse is capable of overcoming occasionally.

TABLE V.

Table of the performance of horses upon the Team Colliery Edge-rail-road, where a horse travels with four loaded carriages down the plane in summer, and returns with the same number empty; and with three carriages in both directions in winter. Weight of loaded carriages 8,540lbs. friction 40lbs., empty carriages 2,604lbs. friction 14lbs.

Resistance with four carriages. Resistance with three carriages.

Total resist-
ance downl
the plane
in lbs.

Gravity of
the empty

Total resist

ance up

in lbs.

123

The horses employed upon the above Railroad are not so strong and heavy as those