Before reaching the main-pipes, the pressure of the gas is regulated by the governor. In small establishments, the governor is very frequently dispensed with, and the pressure adjusted with sufficient nicety by the regulation of the outlet valve. The governor consists of a small gas-holder, the inlet-pipe to which is placed in the center of the tank, and terminates with a plate having a circular °rill& in its center. In this orifice hangs a cone, which is attached to the crown of the small holder. When the gas is issuingg• slowly, the holder rises, taking with it the cone, and so restricting the orifice by which the gas enters. When the gas issues rapidly, the holder falls, and with it time cone, thereby enlarging the inlet, Many and varied applications of machinery are to be found in the larger gas-works, displaying much mechanical skill, and con tinuous progress in the adoption of means to economize labor, and to facilitate and improve the manufacture and distribution of gas.
The gas is conveyed from the works by main-pipes of cast-iron, to which branch or service pipes are connected wherever a supply is wanted. The miti-pipes require to be skillfully arranged with respect to size, carefully jointed, and laid with as few changes in their inclination as possible; but as such changes arc unavoidable, it is necessary to provide for the removal of water, which, flowing along For the gas in the form of vapor, condenses in the pipes, and lodges at low points. For this purpose, a vessel, similar in construction to the tar-well, is connected to the main-pipe, and the water is removed by a'pump. When little condensation is anticipated, and when there is no risk of the water affecting the flow of the gas, a small pipe merely is attached to the main, with a stop-cock to run off the water. 'The service-pipes should incline towards the main; and where this cannot be attained, provision should, be made for drawing off water.
G(0-fittings. —The small pipes for fitting up the interiors of houses are either of wrought-iron or of soft metal. To insure permanent efficiency, it is of the utmost importance that these pipes should capacious; they should be laid eventy, with an inclination towards the meter; and where the inclination is materially disturbed, a box should be provided for the collection and removal of water.
Gas for street-lighting is usually supplied by contract, a specified burner being used, and the lights being lighted and extinguished at stipulated hours. Lights in private establishments were originally elihrged for on the same system: The uncertainty of such a mode of charge directed the attention of gas-engineers to the construction of meters at a very early period. Accordingly, in 1816, Mr. Clegg took out his first patent for the wet gas-meter, which, as subsequently improved by Ma'am, Crosley, and others, came into general use about the year 1822. Dry gas-meters are now extensively manu factured on lc principle first patented by Mr. A. A. Croll, a gentleman who has also
patented various modifications of the apparatus and processes used in the manufacture and purification of gas, and the utilization of the liquid products.
The wet gas-meter-consists of a hollow circular ease, somewhat more than half filled with water. The measurement is made by the cylinder, a hollow drum or wheel, which revolves on a horizontal axis inside the case, the elasticity of the gas supplying the motive-power. The cylinder is divided into four bers by partitions running in a slanting direction from back to front, and presenting a section of a four-threaded Archhnedean screw. A convex cover is fixed on one end of the cylinder. This cover has an opening in the center, which admits the pipe by which the gas enters the der; the being below the surface of the water, so as to be sealed by it. The pipe, after entering the opening, is turned up, so that its mouth is above the water. The gas thus admitted within the cover, finds its way through a slit into one of the four chambers into which the cylinder is divided. Time chamber which first comes into action is at the moment almost entirely under the water. The gas presses between the water and the partition of the chamber, and, in raising the partition, turns time cylinder on its axis, and bt•ings the chamber above the water, filling it at the same :time. The outlet slit of the chamber is on the side of the cylinder opposite to time inlet slit, and is open to the case of the meter. It is not, however, directly opposite to the inlet slit, but is so arranged that it remains sealed under water till the chamber is completely filled with gas, by which time the revolution of the cylinder has brought the inlet slit of the next chamber above the water, and • it is ready to receive the.gas. The filling of the next chamber carries round the one already filled, causes its descent into the water as it revolves, and completely expels the gas by the outlet slit. Two chambers he la Faction at vile time. -'These chambers are made with great accuracy, and are liable to no variation but the enlargement caused by the evaporation of the water, and the consequent depression of the water-line. On the trout of the case of the meter is placed a box, into which the axis of the cylinder extends, having a spiral worm-wheel on its end. The worm-wheel communicates motion to an upright spindle, which again moves the train of wheels by which the handles of the index are worked. The front box also contains the filling and overflow pipes for the supply and adjustment of the water, the entrance-chamber by which the gas is admitted, and in which the float-valve is placed. This valve is supported and kept open by a float which descends, closes the valve, and off the gas when the water is depressed too much.