Trials of Portable Steam-Engines at Cardiff. 07 
through a stufSng-box, but has formed on it a small cone, ground in steam- 
tight. The cone is kept up to its seat by the pressure of the steam, and by a 
small brass spiral spring. 
The spindle is cjiused to oscillate by a rod passing through guides, and 
carrying a friction-roller at its forward end. This forward end bears against a 
double steel cam, made on a gun-metal " sleeve," sliding on the crank-shaft. 
The " times " of the cam are uniform for opening, but vary for shutting 
according to the endway position of the cam upon the shaft, and this position 
is regulated by the governor, with which the cam is. connected by suitable 
levers. It will be seen that this is applying to a portable agricultural engine 
the governor and cam motion, devised, it is believed, originally by Field, and 
shown in the 1838 edition of Tredgold ' On the Steam-engine.' 
The return-motion of the rod is produced by a spring, acting on a collar on 
the rod, and contained in a guide-box through which the rod passes ; there is 
also an indiarubber buffer, to prevent concussion and noise. There is no 
throttle-valve or regulator, nor other implement than this gridiron slide, to 
be acted on by the governor to control the pace of the engine. Messrs. 
Davey, Paxman, and Co. point out that, as the main slide has a lap to it, 
ample time is given to open the expansion-slide, and thus the cam can be of 
easy curves on the opening sides, and that it is at the time of opening alone 
there is really a pressure of steam on the expansion-slide ; whilst, when the 
slide has to close, it may be done very suddenly, because at that moment 
there is practically as much pressure of steam on the one side of the expansion- 
slide as the other, and thus very little suffices to close the slide. 
The feed-pump is immediately under the crank-shaft, and is worked by its 
own special eccentric. 
The regulation of the water is made by a cock in the suction-pipe, which 
draws from a pail in the usual manner. There is a branch inserted in the 
exhaust-pipe near the cylinder, with a stop-cock, by which a portion of the 
waste steam can be conveyed into the pail to commence the heating of the feed- 
water. 
A pipe proceeds from the rising clack-box of the feed-pump. This pipe is 
made of copper, and is one inch in diameter ; it circulates in the exhaust-steam 
pipe, which is of a flattened section, so as to lie in the thickness of the cleading 
on the top of the barrel of the boiler. There are 2\ feet area of the copper- 
pipe exposed to the waste steam. The feed-pipe next passes into an annular 
wrought cylinder, placed in the root of the chimney and in contact on both 
sides with the heated gases as they pass up, before mingling with the exhaust 
steam, the nozzle for which goes through the interior of this cj'linder. 
The bearing- wheels have wrought-iron spokes, cast into bosses, and cast also 
into a rim of a T section. The bosses are cast on chills. The hind wheels 
are fitted on a wrought axle, attached to the front side of the fire-box, but 
cranked horizontally so as to bring the centre of the wheels further back than, 
the forward side of the box. The front wheels are also fitted on a continuous 
wrought axle, fastened to a wooden bed. The perch-pin passes through a 
wrought piece, attached to the under side of the fore part of the barrel of the 
boiler. 
There is a stay-rod to the bottom side of the perch-pin ; the limit of locking 
is made by stop-plates. 
This engine, on trial ran for 4 h. 20 m. of actual time, and for 4 h. 18 m. 12 s. 
of mechanical time, giving a consumption of 3'25 lbs. of coal per brake horse- 
power per hour. 
The average temperature at which the feed-water entered the boiler was about 
186° ; the quantity that would have been evaporated from 212° was 1852 lbs., 
equal to 11-02 lbs. of water per lb. of coaL 
The engine — although the governor, being very sensitive, " hunted " — worked 
F 2 
