It has been usual, in practice, to allow half a cubic foot of coal gas per hour for ;he supply of a light equal to that of a mould candle of six to the pound, and of which one pound will, when the candles are burnt singly, last 40 hours. If the gas, however, is properly prepared, and burnt under favourable cir cumstances, it does not, in point of fact, require above one-third of a cubic foot to produce such light, as will be hereafter shown. But, taking the common allowance, the sizes of pipes necessary for transmitting gas to supply various quantities of light, under the pressure of a column of water, of from five-eighths to three-fourths of an inch, and making very ample allowance for friction, may be stated as follows : It frequently happens, where gas-lights are used, that the times and periods of burning them are very irregular ; thereby rendering the quantity of gas consumed a matter of uncertainty, subjecting both the manufacturer of the article and the consumer to the liability of not being fairly dealt with by one another. To remedy this evil, and generally to as certain the quantity of gas manufactured, different modes of measuring it have been proposed. Gaso meters, suited in size for each consumer, and filled from time to time with gas from proper feeding pipes, though they would answer the intended pur pose, are objectionable on the score of expence, and the room they would occupy, and the trouble, which would be considerable, of attending them; and though it is by no means impracticable to construct such, with a self-acting apparatus attached, for fill ing it, and registering the quantity of gas admitted, yet the cost would, in most cases, more than coun terbalance all advantage to be derived from it.
A self-registering gas meter, of a cheap, efficient, and generally applicable construction, would be an object of considerable importance to manufacturers of gas. In the Repertory of Arts for February 1817 is described an exceeding complex apparatus for this purpose ; which, as it has been abandoned in practice by Mr Clegg, the patentee, need not be explained here. A much simpler and better ma chine for this purpose is described in a late work (Peckston on Gas-Lighting), and of which sections are given in Plate LXXXII. fig. 12, where c c re presents the outside casing, in form of a flat cylin drical drum, having a bent tube, a, inserted at its centre, for admitting the gas, and a branch, b, for conveying it away ; g g, are two pivots, one sup ported from the tube a, and the other from an ex• ternal water-tight cup, projecting from the outside casing, and in which is contained a toothed wheel, h, fixed upon the pivot, and connected with a train of wheel-work (not shown in the figure), to register its revolutions. The pivots are fixed to and support a cylindrical drum-shaped vessel, d d d, having open ings,e e e e; internal partitions,ef, ef, ef, ef; and centre piece ffff • all of which will be understood best by inspection of the figure. The machine is filled with water (poured in at h) up to the level of i ; and gas being admitted under a small pressure at a, it enters into the upper part of the centre piece, and forces its way through such of the openings, f, as are from time to time above the surface of the water ; and, by its action upon the partition nearest in contact with the water (to the right hand of that figure in which all the partitions and openings are shown), a rotatory motion is produced ; the gas from the opposite chamber being at the same time expelled by one of the openings, e, and escaping at b, as before-men tioned.
The quantity of gas discharged by this machine in any given time, depends not only upon its internal dimensions, and number of revolutions made, but also upon the level of the surface of the water within it ; and, as such discharge of gas will be greater or less, as the quantity of water is less or more, attention to its being kept at a proper level is of the first' conse quence to the due action of the meter; and for this reason, means must be employed to insure a supply of water, and a suitable outlet provided, to prevent its accumulating in an undue quantity.
For the combustion of gas, burners, of many dif ferent descriptions, have been used, and the gas made to issue through apertures of almost every variety. Experience, however, has proved, that small circu lar holes, of from one•fortieth to one-sixtieth of an inch diameter, are most advantageous ; and these are disposed in various figures, so as to form lights of one or more jets, and in circles to resemble the burners of the argand lamp.
Particular attention should be paid to construct burners so as to allow the atmospheric air to come freely in contact with the flame ; and, for this pur. pose, when a single jet or light is wanted, the perfo. ration may be made at the point of a small cone, as at a, fig. 9 ; and, for additional lights, other aper. tures, b b, are added near its base ; such, having three flames or jets, as represented, have been named cockspur lights. Fig. 10 is a bat-wing burner, where the flame issues from a narrow alit cut across its tbp.
When lights are required equal in intensity to four or more candles, the arrangement of the holes in a circle, with a central opening to admit atmosphe ric air, and with exterior cylindrical glass, as in the argand lamp, is to be preferred ; and burners giving the light of 10, 15, 20, or a greater number of candles, may be advantageously used on this con struction, varying the diameter of the luminous ring according to the number of apertures required. Fig. 11 is a full-sized representation of a burner with 12 boles, c c, having an air tube, d, in the centre of half inch diameter ; a, the branch through which the gas is admitted into the cylindrical cavity, 6 6, in which it circulates during its passage to the orifices c c; this burner may, with propriety, be used to give the light of six or eight candles. Much smaller ones, where the air-tube, d, is less than about three-eighths of an inch, do not answer well; as the atmosphe ric air is apt not to circulate through them, and the flame unites, in consequence, into one smoky mass.