" It was much to be regretted, that the experiment with the Novelty could not be continued sufficiently long to ascertain the power of raising steam by this method ; the inquiry was of the utmost importance. Theoretically consi dered, we are of opinion, that this mode of generating steam is more econo mical in point of fuel, than in engines, the combustion of the fire of which is kept up by the rarefication in the chimney; but there are practical objections to set against this, of which the destruction of fire-bars, and the power required to work the bellows, are not the least. We say theoretical, because, suppose two generators, the area of the grate-bars, extent of radiant, and communicative surface, are in both the same, 'except the area of exit pipe into the chimney, which, with the generator worked by the bellows, is one half of that by exhaus tion of the chimney. If the same quantity of air pass through the grate-bars in each, that with the bellows will necessarily be in a more comprelised state, to force the same quantity of heated air through the narrow exit ; and this com pressed state of the heated air will, of course, cause more of the caloric to be abstracted than in the other case ; for we suppose the temperature reduced to the same, in both cases, in the exit pipe. For if the heated air, in both cases, pass into a chimney of the same area, and equal to that of the exit pipe from the generator, on the exhaustion principle; the temperature of the heated air being supposed to be the same, in both cases, in the exit pipe : the heated air from the generator with the bellows will, therefore, have to expand itself in the chimney, into twice its volume, which will, of course, reduce its temperature below that of the other ; thus proving a more complete abstraction of the heat. The only question is, whether the disadvantage in practice, consequent upon the operation of such a principle, does not counterbalance any advantage gained in the economy of fuel ; and this we must leave to experience to determine.
" The question between the two modes, however, assumes a new charac ter since the application of the steam from the cylinder to create a current of air in the chimney ; as in that case we can, by the use of a greater number of smaller tubes, reduce the temperature so low, until, if advisable to do so, it is equal to that of the water in the boiler. And it then becomes a subject of inquiry, which of the two modes occasions a greater loss of power in obtain ing the necessary current of air; the working of the bellows m the one case, or the loss of power by the obstructed passage of the steam into the chimney, in the other.
"It is perhaps necessary, after the above disquisition, to explain, so far as we are able, the cause of the failure of the Novelty engine at the Liverpool experi ments ; to show that it arose from no defect in the principle, but only in the construction of that engine. It will be seen by the sketches of this engine, that the flame and heated air, after leaving the fire,passed through the winding pipe of the horizontal generator. The generator was only 12 inches diameter,
and there were three folds of the flue-tube within it, in diameter from 4 inches at one end, to 3 inches at the other; very little space was therefore left between the flue-tube and the top of the generator. The temperature of the flame within this tube, when the engine was running at a quick rate, would be very great, especially where it left the upright generator ; and the evolution of heat would, therefore, be so rapid, that theof the steam out would prevent the water from flowing along this ; and the consequence was, that the flue-tube got dry, and either collapsed with the heat and pressure, or gave way at the joint. This, it will be seen, however, arises from no defect of principle, and was easily remedied." The performance of the improved locomotive engines upon a level railway, has been estimated at from 30 to 40 tons, moved at the rate of 15 miles an hour; according to' which the following table, reduced from Mr. Wood's calcu lations, will show the quantity at diferent Inclinations of plane.
The following extracts from the newspapers (which we believe are substan tially correct) afford an account of some interesting experiments, which show what the locomotives and the railway are capable of.
"On Saturday, the 4th of December, 1830, the Planet engine, Mr. Steven son's, took the first load of merchandise which has passed along the railway Erom Liverpool to Manchester. The team consisted of 18 carriages, containing 135 bags and bales of American cotton, 200 barrels of flour, 63 sacks of oat meal, and 34 sacks of malt, weighing altogether 51 tons, 11 cwt. 1 quarter. To this must be added the weight of the waggons and oil-cloths, 23 tons, 8 cwt. 3 quarters. Tender, water and fuel, 4 tons, and 15 persons on the team, 1 ton, making a total weight of 80 tons, exclusive of the engine, about 6 tons. The journey was performed in 2 hours and 54 minutes, including three stoppages of 5 minutes each (one only being necessary under ordinary circumstances), for oiling, watering, and taking in fuel ; under the disadvantages, also, of an adverse wind, and of a great additional friction in the wheels and axles, owing to their being entirely new. The team was assisted up the Rainhill inclined plane by other engines, at the rate of 9 miles an hour, and descended the Sutton incline at the rate of 164 miles an hour. The average rate on the other parts of the road was 124 miles an hour, the greatest speed on the level being 154 miles an hour, which was maintained for a mile or two at different periods of the journey."—Liverpool Paper.
The annexed experiment Shows the velocity of motion that had been attained on the railway at the period mentioned.
"The journey between the two places was on the 23d of November (1830) performed by the Planet engine in 60 minutes, including 2 minutes, the time employed in taking in water on the road, as usual.