(206.)

In the boiler to be used in the steam carriage projected by Mr. Walter Hancock, the subdivision of the water is accomplished by dividing a case or box by a number of [Pg437] thin plates of metal, like a galvanic battery, the water being allowed to flow between every alternate pair of plates, at E, fig. 118., and the intermediate spaces H forming the flue through which the flame and hot air are propelled.

In fact, a number of thin plates of water are exposed on both sides to the most intense action of flame and heated air; so that steam of a high pressure is produced in great abundance and with considerable rapidity. The plates forming the boiler are bolted together by strong iron ties, extending across the boiler, at right angles to the plates, as represented in the figure. The distance between the plates is two inches.

There are ten flat chambers of this kind for water, and intermediately between them ten flues. Under the flues is the fire-place, or grate, containing six square feet of fuel in vivid combustion. The chambers are all filled to about two thirds of their depth with water, and the other third is left for steam. The water chambers, throughout the whole series, communicate with each other both at top and bottom, and are held together by two large bolts. By releasing these bolts, at any time, the chambers fall asunder; and by screwing them up they may be all made tight again. The water is supplied to the boiler by a forcing-pump, and the steam issues from the centre of one of the flues at the top.

These boilers are constructed to bear a pressure of 400 or 500 lbs. on the square inch; but the average pressure of the steam on the safety valve is from 60 to 100. There are 100 square feet of surface in contact with the water exposed to the fire. The stages which such an engine performs are eight miles, at the end of which a fresh supply of fuel and water are taken in. It requires about two bushels of coke for each stage.

The steam carriage of Mr. Hancock differs from that of Mr. Gurney in this—that in the former the passengers and engine are all placed on the same carriage. The boiler is placed behind the carriage; and there is an engine-house between the boiler and the passengers, the latter being placed in the fore part of the vehicle; so that all the machinery is behind them. The carriages are adapted to carry 14 [Pg438] passengers, and weigh, exclusive of their load, about 31⁄2 tons, the tires of the wheels being about 31⁄2 inches in breadth. Mr. Hancock states, that the construction of his boiler is of such a nature, that, even in the case of bursting, no danger is to be apprehended, nor any other inconvenience than the stoppage of the carriage. He states that, while travelling about nine miles an hour, and working with a pressure of about 100 lbs. on the square inch, loaded with thirteen passengers, the carriage was suddenly stopped. At first the cause of the accident was not apparent; but, on opening one of the cocks of the boiler, it was found that it contained neither steam nor water. Further examination proved that the boiler had burst. On unscrewing the bolts, it was found that there were several large holes in the plates of the water-chamber, through which the water had flowed on the fire, but neither noise nor explosion, nor any dangerous consequences, ensued.