686 
Report on the Trials of Portable 
valve spindle itself is balanced by spiral springs, acting througli a cross- 
head, and in a direction opposite to that of the steam pressure, upon the 
sjiindle in question. 
A positive motion would, of course, be preferable to an arrange- 
ment needing so many safeguards, but the "Farcot" cut-off 
lends itself to the necessity of reversing — a sine qua non in a 
traction engine ; and this is, presumably, the reason for its 
adoption by Mr. Foden. The high and low pressure cylin- 
ders have each a separate link-motion and reversing lever, 
so that the cut-off in the large cylinder can be adjusted inde- 
pendently of the " Farcot " cut-off in the small cylinder, 
while, on the road, the two levers can be coupled so as to act 
together. 
There are two water-tanks, one situated under the barrel of 
the boiler, the other under the foot-plate. The former tank acts 
the part of a feed-tub, receiving the condensed water from the 
heater, but, instead of a bye-pass arrangement, the suction pipe, 
which draws from the tank in question, is provided with a cock 
to regulate the supply. The pump delivers into an inch pipe 
which makes four runs of a chamber occupying nearly half the 
forward length of the boiler, and finally travels through a coil of 
seven turns (or about 43 feet length of 1-inch pipe) placed in 
the smoke-box. A portion of the exhaust steam is further led 
back to the service-tank under the foot-plate, making it hot 
for the stoker, but contributing, with the remainder of the 
arrangements described, to supply a very hot feed. 
The engine, as exhibited, had only one road speed of 27 to 1, 
but could be fitted with a quicker gear of 16 to 1. The axle 
of the travelling wheel, together with the gearing, is carried on 
helical springs, upon which the weight may be thrown, or from 
which it may be removed, at pleasure. The travelling wheels 
have all cast-iron tires and hubs, with splayed spokes of flat 
wrought-iron, while a small chain barrel, hauling upon locking 
chains, and operated by a worm wheel, forms the steering gear. 
When required, steam can be admitted to the low-pressure 
as well as the high-pressure cylinder, by an arrangement which 
was described and figured on page 541 of the last volume of the 
' Journal.' 
Instead of an ash-pan damper, the chimney is provided with 
a sheet-iron throttle-valve, probably the best place, in a trial, to 
check the draft, inasmuch as it affords the driver an opportu- 
nity of closing the chimney aperture at the moment of opening 
the fire-door for the purpose of firing. 
Mr. Foden elected to run at a speed of 156 revolutions, and 
a pressure of 250 lbs., with a brake-load of 18-horse-power. 
The engine was fired by one of his sons, who, though a lad in 
