Fig. 4, Plate LXXXIII., represents the axis of the pulley c, working upon friction rollers (a a, with their support 6) of the common construction. In fig. 7, the axis of the gasometer works upon a sector somewhat similar to fig. 3 reversed ; but this form renders it necessary that the axis shall be kept in its proper situation by means of a double or forked frame as shown, and thereby causing a certain degree of fric tion from which fig. S is exempt.
The manner of conveying the gas into and out of the gasometer, delineated in figs. 1, 2, 5, is the simplest and best when it can conveniently be prac tised. It, however, sometimes happens that access to the lower part of the pit or cistern is difficult to be obtained, and other means have to be resorted to. Swivel or flexible jointed tubes, arranged so as to rise and fall with the gasometer, though they an swer well enough on a small scale, are with difficulty made of large capacity so as to have little friction. We have seen jointed tubes connected by means of water-lutes extensively used, and which answer well the intended purpose; one of these is represented in fig. 6, a being the pipe where the gas is introduced; b a vertical pipe capable of a small angular motion on the axis or support c, and connected with a by means of a water-lute joint ; its upper end is also connected in a somewhat similar manner to one end _ of the pipe d, and again at e, another moveable wa ter-joint is,placed ; f is the pipe connecting with the top of the gasometer; g a regulating radius bar centered to a bracket attached to the pipe d, and working on a fixed pivot at i. The gasometer rising or falling, carries f along with it, and in the rest of the apparatus a motion is induced, corresponding with the connection of the different parts.
Having more or less minutely described different constructions of gasometers, it may be proper to ex plain the nature of such contrivances as have been introduced to render uniform the pressure of the gas issuing from such as do not possess the means of re gulation within themselves.
Fig. 17. Plate LXXXI. represents one of these go-' vernors, consisting of a crooked tube a a a a, with al conical valve seat fixed in it at b; c, a valve fitting the seat when shut, and having a stem carried upwards and connected with the inverted conical vessel d d; e e, an exterior vessel, in which water is contained to the level represented. The gas enters at the bottom
tube, and passing through the valve, escapes at the other horizontal extremity of a, and at the same time fills the upper part of the inverted vessel d d, and raises it more or less according to the pressure and velocity with which the gas enters; thereby par tially closing the valve as the pressure increases or diminishes, and thus regulating the quantity of gas discharged through the machine.
Fig. 18 is another regulator or governor, not dif. fering in principle from the former ; the gas enters at a; 6 is the valve seat; c the valve with stem connected to the , inverted vessel d, which is sus. pended in a cistern of waterff, and moves neon a pivot at e. The action of this apparatus is similar to that of the former one, and of the two, it is of a construction more likely to answer the intended purpose.
Regarding the distribution of gas for the put% poses of supplying light in distant and different si tuations, a few remarks may be made.
The pipes or tubes for this purpose are best when made of cast iron with socket joints, and put to gether with lead ; and for smaller sixes than what are manufactured of cast-iron, welded or brazed plate iron connected by screws, may be used. Cop per tubes are objectionable, on account of the action of the gas upon that metal if not perfectly purified ; those of block-tin, lead, and some mixed metals, an swer *ell enough when made sufficiently strong to resist external injury.
As the gas always carries along with it a quantity of aqueous or other vapour, it is requisite to lay the pipes so, that this, when condensed, can be collected and drawn off from time to time. A small declivity is, therefore, to be made towards one or more points, where cocks, closed vessels, or inverted siphons, are to be placed, to collect and take off the water, &c. accumulating. For stopping off the gas in large pipes, waterlute valves are generally used, one of which is represented in fig. 16, wherein a is the valve, formed like an inverted cup, with rod (working through a stuffing box) attached, and handle above ; b, an annular cavity containing water, into which the valve, when shut, falls. This is about the simplest, and probably the best form of valve, and though others of a more complex nature have been used, they do not appear better adapted for the required purposes.