54. Some meters are provided with a gauge similar in construction to that shown in fig. 15. As shown it is a box, rect

METER

CASE

FIG. 15.

angular in shape, attached to the meter case, and in communication with the interior thereof at a point x, below the water-line of the meter. P is a pipe connecting the box with the inlet of the meter, so that the inlet pressure of the gas may act within the box. O

is a vertical pipe screwed through the bottom of the box, and rising therein to the needful height for its top to coincide with the water-level. The bottom of O is sealed in a lute from which a pipe extends to a sink or drain. A meter which is provided with such a gauge as this cannot be overcharged with water, for any excess which may be run into the meter at once flows away through O. It is usual with large station meters in gasworks to keep a constant stream of water flowing into the meter, for the purpose of maintaining the water-level within the measuring wheel as equable as possible under varying rates of speed (36), and also for the purpose of keeping the water in the meter in as clean a condition as possible. The box being subject to the inlet pressure, and the top of the pipe O coinciding with the line of true measurement within the wheel, it will be apparent that when the working speed of the meter is increased, the incoming water soon restores the true level, and that when the working speed slackens the increased rapidity of the outflow soon disposes of any excess.

D

55. Another form of water-level gauge is shown in fig. 16. This form was devised by Mr. Mills, Meter Inspector of the Metropolitan Board of Works, at Westminster. It serves simply as a

O

FIG. 16.

main charged, thereby ing the escape of gas.

seal box, and is acted on by the outlet gas through the hole G, the water entering the box from the meter through a lower hole. The pipe P is cut to the water-line, and the water flows into C, thence through the channels D, E, into the outer chamber F, and out at the spout. The advantage of this box is that an excess of water cannot be run off, or syphoned out from F, for, although it may be syphoned from E, F, yet, as the water column is broken above E, the channels D C represerving the true level and prevent

There are several other forms of over-flow water-level gauges, but those which have been described embrace the principles on which all are constructed.

APPARATUS REQUIRED FOR THE VERIFICATION OF GAS METERS.

56. ONE OR MORE INSPECTION STANDARD GASHOLDERS.

In towns where a large number of meters will require to be tested, four or even sia gasholders may be needed, but in most cases two will be sufficient, and the most useful are those of ten cubic feet nominal capacity. In some cases a five-feet holder is used for testing for soundness, and a ten-feet holder for the test for registration. One-foot holders are useless for meter testing.

TWO LENGTHS OF FLEXIBLE TUBE FOR EACH HOLDER.

These are fitted to meters with screwed brass sockets to receive cones of the several sizes required to fit the unions of gas meters. One of these tubes is attached to the outlet of the gasholder, and the other to the pipe which conducts gas from the meter under testing.

A PROVING-BENCH.

This may be a strong table of wood with a lead covered, or a slate top, which must be perfectly level, or it may be a cistern about 5 ft. 6 ins. to 6 ft. long, 2 ft. 6 ins. wide, and 2 ft. 6 ins. deep; its elevation to the needful height being effected by placing it upon blocks or brickwork, leaving a part of the space below open from back to front. The edge of the front plate of the cistern should be one inch above, and the edge of the back and end plates three inches above the level of the top slab. The top slab should be 1 in. or 14 in. thick, the edges, in the direction of its length, should be rebated, and the upper surface be planed perfectly flat. The width of the top should be 3 ins. less than the internal width of the cistern, and it should be so adjusted as to leave an opening along the back of the. cistern 2 ins. wide, and an opening the front of the cistern 1 in. in width. These openings should be covered with strips of perforated zinc, fitting upon the rebates of the top and into saw-cuts in the back and front plates. The gratings, thus formed, permit the free flow of water into the cistern when wet meters are being emptied, after having been tested. The raised edges round the top of the cistern prevent the slopping over of water. The cistern should be fitted with water-supply pipe and ball-cock, and with an overflow or waste-pipe. As the water has to be drawn from the cistern for the purpose of charging wet meters, a small

pump is also required, which may be fixed on the cistern as shown, or be placed in any other situation which may be more convenient.

ONE OR MORE FLOATS.

Each float consists of a length of 2-inch iron tube, mounted along its length by 20 brass cocks, each supporting a burner. The 2-inch tube terminates with an 1 blow-off cock.

TWO OR MORE GAS TORCHES,

each with 10 feet of flexible tube.

A CLOCK,

indicating seconds, minutes, and hours, striking at the end of each minute (when required to do so), and going eight days.

A PAIR OF DOUBLE BLAST BELLOWS.

These are only required when air is used for testing meters instead of gas.

THERMOMETERS.

For taking the temperature of air and of water.

57. A convenient arrangement for two gasholders is shown in the illustration. The proving-bench stands between two gasholders, one of which is for use with gas, while the other on the right, is for use with air, its inlet being connected to a pair of double-blast bellows. From the outlets of the holders, the flexible tubes are extended and terminate in the brass sockets, into which the cones, of the size requisite to fit into the unions of the meters about to be tested, are screwed. These tubes and cones serve to connect the gasholders to the inlets of meters. Similar connections are needed for the outlets of meters, and are shown on the pipes which descend to the floor, and on the gas side are continued to the float of lights enclosed in the chimney breast. On the air side the pipes should be extended to some convenient point of dis