402 
EXPLANATION OF THE PLATES. 
hh, Tail pieces connecting the rollers with the slides. 
i i, Springs tending to force the tail pieces with the slides inwards. 
k k, Rods for attaching the tail pieces to the slides. 
l, Bearings for the hollow axle. 
m, Train of gearing communicating with the governor n. 
The connection of the latter with the throttle valve in the entrance steam pipe 
is shown at o. 
p, Is a wheel taking into the intermediate wheel, m, working a pump for supplying 
water to the boiler. 
A, Is a sluice cock for letting on the steam; and 
B, A double cock lubricator. 
Fig. 2 is a front elevation, the engine in this figure being supposed to have moved 
half a turn to the left hand from the position in which the parts are shown in the 
former figure. 
Plate LXXII. Fig. 1 represents a side elevation of the engine, showing all the 
parts in similar positions to those represented in the plan or horizontal view. 
Fig. 2 is a longitudinal vertical section taken through the cylinder d, steam stop 
(or what may be called) piston q, hollow axle r, &c., the connection of the slides s s, 
with the tail pieces h A, by the rods k k, being also shown in section, in order to 
render it more evident. The hollow axle r has a partition t, shown in the middle, 
dividing the entrance from the exit steam way, as may be more clearly seen at 
figs, 3 and 4. In this figure the entrance steam way is shown in section at u, and 
the exit v, in dots ; the cam or wiper f as also the slide race or grooved way, are 
likewise shown in dots. The piston (marked q in the figure) is composed of several 
pieces of metal connected together as shown, the manner of fixing it between the 
hollow axle r and the inside of the cylinder being as follows. A standard piece, 
as at w, may be cast with the hollow axle r, but is preferred to be screwed firmly 
to it, to which the blocks of metal x are fastened, also with screws, but which 
screws, in this case, are passed through slots, in order to allow of a little play; the 
connection of the blocks, x, with the pieces y, which fit closely against the internal 
periphery of the cylinder, is formed by a tongue on the former, fitting into a cor 
responding dovetailed groove in the latter, the whole being kept perfectly tight 
during action by a spring, placed as seen by dots in fig. 3. The rotatory motion of 
the engine is effected by the elastic pressure of the steam admitted through the 
axle r, by the aperture u, into the cylinder d, exerted between the stationary steam 
stop or piston and each slide alternately as they are brought up the groove z into close 
contact with the axle r, by the action their respective rollers, g, receive in working- 
over the stationary cam or wiper f In this figure, the dotted line on the right hand