them having been in regular work since May 1879, up to date, say four years, or eight years' ordinary work of twelve hours per diem: which is a fair test of their lasting properties.

The centre of the fire-box is necessarily open to the uptake or chimney, and the flame and heated gases would thereby pass rapidly

away; but, to prevent this, and to distribute them amongst the tubes, this open space is partially blocked up by a cast-iron chamber or superheater D, Fig. 1, into which the exhaust steam is led by the two pipes A and B, Figs. 1 and 3 (one from each cylinder), consequently (this chamber being always at a very high temperature, owing to its near proximity to the furnace) the steam is dried, and also superheated and rarefied to a high degree after leaving the cylinders, and immediately before it issues into the atmosphere up the funnel by means of the pipe C, Figs. 1 and 3, and when passing up the funnel has to intermix with the whole volume of heated gases from the furnace; at the same time its velocity upwards sets up an induced current and causes a strong artificial draught in the furnace.

The waste steam from the safety valves is also led by the pipes A and B to the superheater D, Figs. 1 and 3, and undergoes exactly the same process as the exhaust steam does. The superheater D, Figs. 1 and 3, has a conical pipe cast in its lower end, projecting upwards, and passing up the inside of the exhaust pipe. This pipe is enlarged at its lower end, and is fitted with a perforated grating or grid, made from cast iron, fire-brick, or any refractory material, to arrest sparks; inside this pipe is fixed a steam-jet pipe, so as to be either in direct communication with the boiler or coupled to the main steam-pipe, between regulator valve and cylinders, at pleasure. In direct connection with the steam supply for this jet is another circular ring or jet, consisting of a pipe bent round the mouth of the blast pipe, and perforated on its upper side with a number of minute holes.

These steam jets when open cause a strong induced current of heated gases from the furnace to issue from the mouth of the internal pipe, which is just level with the end of blast pipe C, Figs. 1 and 3, the two pipes forming an annular space from which the exhaust escapes, the heated gases being injected right into the centre of said space, and thereby mixing thoroughly with the already superheated steam (the ring jet causing a current externally) in such a manner as to render the steam invisible when issuing from the funnel into the atmosphere, except under the most abnormal states of the weather, say frost and fog or snow combined.

The annular space inside the uptake is filled with fire-clay, which protects the boiler plate from the action of the flames, above the water-line; this action has always been a source of trouble in all

FIG 2

other vertical boilers at this point, causing rapid deterioration, but has been effectually dealt with by placing this fire-clay non-conductor here as shown.

In case a tube "burns out" it can easily be replaced by any ordinary labourer or engine-man at a very insignificant cost.

Fig. 2 is a section of crown plate of fire-box with both internal "circulating" tube and outer tube in situ.

The exhaust steam, before being led into superheater D, Figs. 1 and 3, by pipes A and B, Figs. 1 and 3, is passed through a box or vessel, F, Fig. 4, on each side of boiler, which intercepts any water, due to condensation, from the cylinders, which water is led to the ground by means of two pipes, each provided with a stop-cock. Each cylinder has a waste water-cock and pipe leading also to these boxes.

The engines are of the ordinary "inverted vertical type," with link-reversing gear, which gear is acted on by the automatic governor, as follows, viz.: When the regulation speed allowed by the Board of Trade is exceeded, the governor opens a steam valve on the boiler, and admits steam to two pistons; one reverses the valve gear of the engines, and the other applies a brake to the wheels, both acting in concert and simultaneously.

Under the control of the driver is a powerful steam brake, which can be brought instantly into action on the wheels of the passenger

car.

The steam pistons in this engine are not connected directly to the driving axle as in the "Locomotive Tram Engine," but act directly on a crank shaft, G, Fig. 4, fixed in rigid bearings attached to the frame plates. On this crank shaft is fixed a spur wheel, H, Fig. 4, which gears into another spur wheel, K, Fig. 4, keyed on the driving axle, which axle has a pair of the running wheels, L, Fig. 4, for the road, keyed one on each end, these wheels being coupled in the usual manner to the leading wheels by means of the usual coupling rods and outside crank pins.

This arrangement of spur wheels is a departure from all practice which has gone before for tramway or other geared road engines, inasmuch as they are placed in the centre of the axle and round the teeth transversely across their length, which allows for one end of the axle to lift or fall, as the inequality of the road demands.

In all geared engines hitherto used the spur wheels have been invariably placed on one or both sides of the engine, with the result (owing to the unequal action of the springs on each axle box, caused by the unevenness of the track or line bringing such a powerful cross strain on the spur wheels) that there was constant repairs and renewals of said gearing required; whereas, in this case, with the

spur gear in the middle of the length of the axle and with the rounding lengthwise of the teeth, this source of trouble is reduced to a minimum, never having had a wheel broken or damaged so far.

Hitherto the spur wheels have been made of solid hammered scrap iron forgings, machined all over, with the teeth slotted out of