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 the cylinders into the chamber under the chimney just mentioned. This chamber receiving in the first instance the hot air which rushes from the tubes, and the exterior surfaces of the cylinders being exposed to its action, their temperature is maintained at nearly the same point as the water in the boiler.

These engines are placed upon four wheels, the greater part of the weight, however, usually resting upon two. Thus in an engine weighing eight tons, five tons rest upon the large wheels, and three on the less. The axle of the greater wheels is cranked, and they are kept in a state of rotation by the engine. In some engines, however, the pistons work the four wheels, and in this case the wheels are of equal size, and subject to equal portions of the weight.

At the time when extensive lines of railroad are in progress, calling into action many millions of capital, and the welfare and property of thousands, and when other lines not less extensive are in contemplation, it would be extremely desirable, were it possible, to give an estimate of the regular expense of maintaining and working a railway, which has been already successfully established, and the advantages arising from it as a great comercial speculation. But there are circumstances attending the Liverpool railway which render such an estimate impracticable. The proceedings of the company and their engineer, from the moment when the earth was first opened on the projected line, to the present time, cannot be justly regarded in any other light than as a series of experiments, each successful in itself, but each only the forerunner of improvements by which the previous methods and expedients were superseded. And this was naturally to have been expected, when it is considered, that no great experiment of this nature