Part 25 (1/2)

The labour of feeding the retorts with coal and rely severe In the illustration on p 400 (raph taken by Mr F Marsh of Clifton) we see a h the iron doors at their outer ends

Autoasworks for both operations

One of the198 Theon rails along the face of the retorts Coal falls into a funnel at the top of the telescopic pipe P fros, H H, controlled by shutters The coal as it falls is caught by a rubber belt working round part of the circue wheel W and a number of pulleys, and is shot into thethe handle which opens the shutter of the hopper above the feed-tube, and switching on the 4 hp electric motor which drives the belt and e a retort 20 feet long in twenty-two seconds

[Illustration: FIG 198--De Brouwer autoer]

A GAS GOVERNOR

Soas-jet, which a few hours before burned with a somewhat feeble flame when the tap was turned fully on, now becoorous, and finallysound This is becausethe house have been turned off, and consequently there is a greater a, which therefore feel an increased pressure As a as in the ularity of the delivery froasometer, and partly to the fact that the nuether It asoher pressure than those at the other end The gas stored in the holders may be wanted for use in the street lamps a few yards away, or for other lamps several miles distant It is therefore evident that if there be just enough pressure to give a good supply to the nearest lamp, there will be too little a short distance beyond it, and none at all at the extreh pressure to overcoive just enough gas at the extreme end It follows that at all intere quality is burned to the greatest advantage, as regards its light-giving properties, when its pressure is equal to that of a coluh, or about 1/50 lb to the square inch

With less it gives a sht, and with more the combustion is also imperfect

[Illustration: FIG 199]

Every house supply should therefore be fitted with a gas governor, to keep the pressure constant A governor frequently used, the Stott, is shown in section in Fig 199 Gas enters froht, and passes into a circular elbow, D, which has top and bottom apertures closed by the valves V V Attached to the valve shaft is a large inverted cup of metal, the tip of which is iovernor is to act is deterhts W, hich the valve spindle is loaded at the top As soon as this pressure is exceeded, the gas in C C lifts theoff the supply Gas cannot escape from C C, as it has not sufficient pressure to force its way through the mercury under the lip of the cup Ias being used up, the valves open and adht, the valves never close completely, but merely throttle the supply until the pressure beyond them falls to its proper level--that is, they pass just as as as the burners in use can consuer size, but working on much the same principle, are fitted to the asometers

They are not, however, sensitive to local fluctuations in the pipes, hence the necessity for separate governors in the house between the meter and the burners

THE GAS-METER

co 200 The air-tight casing is divided by horizontal and vertical divisions into three gas-chambers, B, C, and D Gas enters at A, and passes to the valve chamber B The slide-valves of this allow it to pass into C and D, and also into the two circular leather bellows E, F, which are attached to the central division G, but are quite independent of one another

[Illustration: FIG 200--Sketch of the bellows and chaas meter]

We will suppose that in the illustration the valves are adas to chamber C and bellows F The pressure in C presses the circular head of E towards the division G, expelling the contents of the bellows through an outlet pipe (not shown) to the burners in operation within the house

Sias in chah the outlet The head-plates of the bellows are attached to rods and levers (not shoorking the slide-valves in B As soon as E is fully in, and F fully expanded, the valves begin to open and put the inlet pipe in communication with D and E, and allow the contents of F and C to escape to the outlet Thewheels, visible through a glassin the side of the case As the bellows have a definite capacity, every stroke that they give as has been ejected either froistered by the counter The apparatus practically has two double-action cylinders (of which the bellows ends are the pistons) working on the sa 21) The valves have three ports--the central, or exhaust, leading to the outlet, the outer ones froh channels in the division G

INCANDESCENT GAS LIGHTING

The introduction of the electric arc lalow-laas as an illuent

But the appearance in 1886 of the Welsbach _incandescent as-burners opened a prosperous era in the history of gas lighting

The luas flame depends on the number of carbon particles liberated within it, and the temperature to which these particles can be heated as they pass through the intensely hot outside zone of the flaht is yielded, up to a certain point, with a flaiven temperature To increase the heat of the flame various devices were tried before the introduction of the incandescent mantle, but they were found to be too short-lived to have any coht for ht could be obtained froas independently of the incandescence of the carbon particles in the flaas could be better eent, to raise to incandescence substances having a higher eht than carbon

Dr Auer von Welsbach found that the substances most suitable for incandescent mantles were the oxides of certain rarea cylinder of cotton net into a solution of nitrate of thoriu 99 per cent of the former and 1 per cent of the latter metal When the fibres are sufficiently soaked, the mantle is withdrawn, squeezed, and placed on a as flame and the cotton is burned ahile the nitrates are converted into oxides The mantle is now ready for use, but very brittle So it has to undergo a further dipping, in a solution of gun-cotton and alcohol, to render it tough enough for packing When it is required for use, it is suspended over the burner by an asbestos thread woven across the top, a light is applied to the botto but the heat-resisting oxides

The burner used with a as is es from the jet, with sufficient air to render its combustion perfect All the carbon is burned, and the flah almost invisible, is intensely hot The ht energy This is proved not only by the intense whiteness of thefroreat when the mantle is in position as when it is absent

The incandescent mantle is as lighting is on the incandescent systeland about 40 per cent Wefortunes of invention, that the once dooas-burner has, thanks to Welsbach's mantle, in many instances replaced the incandescent electric lamps that were to doom it

[38] If, of course, there is no safety-valve in proper working order included in the installation