538 
Trials of Traction-Eugines at Wolverliamilton. 
Burrell's 8-horse-power, No. 3661. Fifth, Thomson's vertical 
pot-boiler with iron wheels. Of this type Ransomes, Sims, and 
Head exhibited one engine, No. 2150. 
Reverting to the entire liberty left to exhibitors as to the pro- 
portions of their engines for a nominal horse-power, it may be 
well to compare those proportions with some standard, and the one 
we propose to take is that employed at the Bury Show for single- 
cylinder engines, viz., 10 circular inches of piston area for each 
horse-power. The strokes of the various engines differed so little 
among themselves, none being under 10 inches, and none over 
1 foot, that there is no impropriety in assuming that the feet run 
per minute of piston might be the same in all the engines, the 
difference in the length of the strokes being corrected by a corre- 
sponding difference in the number of revolutions. This being so, 
and the boilers being suitably proportioned, the relative number 
of circular inches given by exhibitors to a nominal horse-power 
would represent the relative value of the engines in point of 
utmost power to a customer. 
Aveling and Porter''s 10- Horse-power Ewjine. — The first engine we will 
describe, as it was the fii'st which was tried upon the brake, is Aveling and 
Porter's 10-horse-powcr engine, No. 7001, price 390Z. The boiler of this 
engine is of the ordinary iiortable engine or locomotive tj-pe, having'a fire-box, 
barrel smoke-box ; and funnel, this latter by-the-by was cast iron, which 
the makers' Insist is much more durable than the ordinary wrouglit-ii'on con- 
struction. The area of the fire-grate is 62 feet ; tliere are 53 tubes, 2j external 
diameter, giving a collective area of 169i feet, which, with the fire-box area, 
35t feet, makes up a total heating surface of 204f feet. The collective area 
for draft through the ferrules of the tubes is '75 foot. The engine is a single 
one ; the cylinder is 1 foot stroke by 10 inches bore = 100 circular inches area, 
thus giving the exact Bury standard of 10 circular inches for each nominal 
horse-power. The cylinder is mounted on the fore end of the boiler. It is 
contained in and forms ]Xirt of a casting, which is at once steam-chest, slide- 
jacket, steam-jacket, and cylinder. The steam on its way to the steam-chest 
passes through the jacket round the cylinder, which jacket is thus always open 
to the boiler. The regulator and throttle-valves are betv/een the steam-chest 
and the slide-jacket. Within the barrel of the boiler a cast-iron baffle-plate is 
placed over the steam outlets, with the view of preventing " priming." Tlie 
crank-shaft is of the bent construction, and is mounted in brasses carried in 
wrought-iron plummer-blocks. These are supported on bracket-plates. The 
outer bracket-plate of each plummer-block is formed by continuing the fire-box 
side upwards (and, as will be seen immediately after, these same sides are pro- 
longed backwards to support the second motion-shaft), the inner bracket-plates 
for the crank-shaft plummer-blocks rise from the top of the fire-box to which 
they are riveted. On the left-hand end of the crank-shaft is a fly-wheel 
driving pulley, from which power can be taken for threshing, &c., and the 
shaft itself is prolonged beyond the pulley to receive a coupling for an universal 
joint-shaft to drive a windlass for ploughing. On the right-hand end of the 
crank-shaft is a pinion, which gears into a spur-wheel on the second motion- 
shaft. This shaft extends across the back of the fire-box, and is carried in 
bushes bolted to the bracket-plates, which, as already mentioned, are the same 
plates as those that are carried up to support the crank-shaft, they being caused 
