The cistern is made of oak or mahogany, for strength and durability; but, for the sake of lightness, the upper work and side-boxes are made of Baltic fir, strength in them being of less importance.
As the valve cannot be made without a rise for the lid to strike against, there is a small step at each of the valves, and the sole is carried through as high as this step, to admit of the water running off when the engine is done working. If constructed in a different manner, the water will lodge in the bottom, and produce much inconvenience in situations where the engine is exposed to frost.
The valve-covers are of cast-iron, fastened down with copper screws, a piece of leather or india-rubber being placed between them and the upper edges of the sole.
The pieces at each end of the sole are of cast-brass, instead of sheet-copper, with soft-solder joints, which are very apt to give way.
The screwed suction cap with iron handle admits the water in two different directions, according as it is open or closed: the one to supply the engine when water is drawn from the cistern, the other for drawing water through the suction-pipe.
The valves are brass plates, truly ground to fit the circular brass orifice on which they fall. The brass being well ground, no leather is used for the purpose of making them tight. The longer they are used the better they fit, and by having no leather about them they are less liable to the adhesion of small stones or gravel. The whole valve is put together and then keyed into a groove in the sides and bottom of the sole, left for that purpose.
The barrels are of cast-brass, with a piston made of two circular pieces of the same metal, each put into a strong leather cup, and bolted to the other. The bottoms of the cups being together, when the piston becomes loose in the barrels, and there is not sufficient time to replace the cups by new ones, they are easily tightened by putting a layer of hemp round the piston between the leather and the brass. This operation, however, requires to be carefully performed; for if more hemp is put into one part than another it is apt to injure the barrels. The barrels are fixed to the cast-iron sole by copper screws, a little red lead being placed between the bottom flange of the barrel and the sole.
When the engine is likely to be dragged over rough roads or causeways, it is of importance to have it set on springs, to prevent the jolting from affecting the working part of the engine, everything depending on that being right.
The engines used in Paris are mounted on two wheels, the carriage and the engine being separate, the latter being dismounted from the former before it can be used. In Paris, where the engines are managed by a corps of regularly-trained firemen, this may answer well enough; but if hastily or carelessly dismounted by unskilful persons, the engine may be seriously damaged. It is also worthy of remark, that the proper quantity of hose, tools, &c., can be more easily attached to and carried on a four-wheeled engine.
In order that the men may work more easily at the handles, and suffer less fatigue, the engine is not higher than to enable them to have the levers easily under their command. The shafts of the levers are of lancewood, being best calculated to bear the strain to which they are exposed when the engine is at work, and they are made to fold up at each end for convenience in travelling.