022 
tfppori on ihc Imptpme.vis 
a rocking-sliaffc, vibrating at rigbt angles to tlie cylinder and 
having its bearing in the central bracket already mentioned. 
This rocking-shaft is armed with a T head immediately over 
the tails of the valve-levers, so that as the shaft rocks one or 
other of the levers is depressed. The outer end of the rocking- 
shaft is fitted with a lever, turned downwards, the length of 
which can be varied by screwing its eye end more or less into 
the end on the shaft, and securing it in any position by a lock 
nut ; it is moved by a connecting rod and second rocking-shaft, 
the outer lever of which is actuated by Proell motion. This con- 
sists of an eccentric keyed on to the crank shaft, and a wide 
strap, the position of which on the sheave is determined by a 
short eccentric rod, actuated by an eccentric formed on a rocking- 
lever placed a little below and to the rear of the crank shaft. 
The eccentric sheave is provided with a cylindrical slide almost 
tangential to the sheave, but a good deal to one side, and along 
this slide the head of the connecting rod actuating the valve- 
lever slides up and down under the influence of the governor, 
which causes the lower rocking-shaft described above to vibrate, 
and, through a short vertical connecting rod attached to one of 
its levers, to cause the connecting rod to follow, the eccentric 
sheave being shifted at the same time by the eccentric move- 
ment already described. The combination of these two motions 
on the valves is such that they open at the same portion of the 
stroke, no matter what the degree of expansion may be, and 
they close at any period that may be necessary to admit suffi- 
cient steam to do the work, the governor regulating the point 
of cut-off automatically. 
The governor is on Proell's system, and is of the inverted 
ball type, with a spring fulcrum concealed in the central coun- 
terweight. The engine works under 80 lbs. steam, will cut-ofF 
from 0 to stroke, and runs at 90 revolutions, indicating at ^ 
cut-off about 48 horse-power. 
Messrs. JEddington (t Steevenson, of Chelmsford, exhibited a 
traction engine of 8 horse-power, together with road roller at- 
tachments suitable for fixing to any action or ploughing engines. 
(Arts. 5588-5589.) 
In the traction, engine there were several special features 
deserving notice. For the power of the engine its Avidth and 
weight were reduced considerably below the jirevailing practice, 
the over-all width being 5 feet 11 inches, and weight 5 tons 
empty ; the construction of the main wheels, which were 5 feet 
G inches diameter by 1 foot 2^ inches wide, was good ; and, so 
far as could be judged merely from examination, the spring 
mounting of the driving wheels seemed likely to accomplish all 
