preservation of the engines, the same defects as gas-coke.

Respecting the distance travelled by the engines in these experiments, the railway from Liverpool to Manchester is generally reckoned 30 miles long, and considered a level; but as a greater degree of accuracy is required in the calculation, and as we wish to deduce from these experiments the really corresponding consumption of coke on a level railway, we must reckon as follows.

One part of the line travelled by the locomotive engines is 29 miles long. If we divide it in three parts, we see that 1 t. drawn from one end of the railway to the other, opposes the following resistances. (See the section of the railway, Chap. V. Art. VII. § 1.)

1 t. at 261⁄2 miles, on nearly a level...................... 1 t. at 1 mile, ascending

or 9, equal (friction and gravity) to 4 t. drawn to the same distance on a level, or 1 t. at 6 miles....

1 t. at 1 mile, descending by the sole force of the

gravity..

Sum.....

ton. miles.

1 at 261

1 at 6

0 0

1 at 32.5

Thus when the engines ascend the plane without help, the work they actually do is equal to the traction of a similar load to a distance of 32.5 miles on a level.

If they ascend the plane with the help of one or more other engines, their share of the load in ascending is on an average only of the whole on

the plane, and thus the work they do is equal to the traction of their load to 26.5 + 2 = 28.5 miles.

This does not include the surplus of resistance owing to the gravity of the engine and its tender in going up the plane. Their average weight being together from 13 to 14 t., the gravity of which on the plane is equal to the resistance of about 40 t. on a level, we see that this fresh effort required of the engine, equals the traction of 40 t. to a mile and a half, which is the length of the acclivity. If therefore the train itself weighs 30 t. without the tender, as is the case with engines that are not helped by additional ones, the work is equal to the traction of that train 2 miles more than the length of the line. If, on the contrary, the load weighs 60 or 80 t., as is in general the case with engines that are helped on the inclined planes, the additional traction of 40 t. for 1 mile, is equal to the traction of the whole load to a mile.

Then for trains that receive no help at the passage of the inclined planes, we must reckon the distance for which the draft has taken place, as equal to 344 miles on a level; and for the engines that are helped on the acclivity, we must reckon the work they have done as equal to the traction of their load to a distance of 29 miles on a level. The difference which exists in these two cases, is of in plus for the unassisted engines. This is the work done by the helping engines when they

are employed, and the surplus of work produced by of the planes.

the

passage

It is from those distances of 29.5 miles and 34.5 miles, that the numbers placed in the eighth column of the preceding table have been deduced in each experiment.

In examining the results contained in that table, we find that they agree with the rule deduced above from the theory of the engine.

For the ATLAS, the average of the experiments made with 25 waggons, gives 119 t. conveyed by 1136 lbs. of coke. Calculating upon this data, and adding for the cases where there has been no help, we find

If we take into account the accessory circumstances, we shall find between the calculation and

the experiment, as complete a coincidence as the nature of the experiments themselves could allow ; for, besides the above-mentioned circumstances, the greasing of the carriages, the quality of the coke, and, above all, the manner in which the fire-place is filled after the experiment, are subject to produce considerable differences, notwithstanding the most scrupulous attention.

The experiments we have related, give the quantity of coke consumed during the trip.

It is however clear, that in the interval between one trip and another, the engine, although at rest, continues to consume a certain quantity of fuel, because its fire must be kept up for the following journey. It is true, that several of those engines, such as the ATLAS, VESTA, and some others, have a particular sort of apparatus, by means of which, while the engine is at rest, the steam that continues to be generated in the boiler may be led to the tender. That steam is then not completely lost, being condensed in the boiler, and serving to heat the water it contains. But all the engines are not disposed in that manner.

Besides, there is in all cases consumed, every morning, a certain quantity of fuel for heating all the parts of the engine and the water of the boiler.

A surplus of consumption must therefore be calculated for those two objects. This is a practical piece of information which will find its place hereafter.

The researches contained in the work, give the solution of all such questions as are most important for the application of locomotive engines to the draft of loads on railways. They give the means of measuring the pressure of the steam; of calculating the load, the velocity, and the proportions of the engines; of valuing the different sorts of resistance they have to overcome; of taking into account the influence of additional circumstances on their motion; and, finally, of knowing their consumption of fuel.

Here naturally our work terminates. However, as a knowledge of these engines cannot be complete, unless we are able to calculate also the expenses they will require for a given draft, we add in an Appendix the necessary information, by means of which that important point may be established.