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EXPLANATION OF THE PLATES. 
PLATES XLIX. and L. 
ENGINES OF HER MAJESTY’S STEAM SHIP MEGiERA. 
Her Majesty’s steam ship Megsera is fitted with Messrs. Seaward’s engines and 
Mr. Samuel Hall’s condenser. 
Plate XLIX. represents an elevation of the engines. 
Plate L. exhibits a section of the same engines, and comprises a delineation of Sea 
ward’s Patent Slide Valves, the principle of which has been described in Art. 451. 
The same letters refer to corresponding parts in both Plates. 
A, Is the boiler, of which— 
a, Is the furnace door. 
a, Grate bars. 
a", Furnace. 
b, Bridge. 
c, Flues. 
d, Take-up. 
e, Chimney, which is surrounded with 
a double casing e, filled with incombusti 
ble and non-conducting matters, calcu 
lated to intercept the heat and thereby 
prevent accident from fire. 
f Water space beneath the flues, suffi 
cient to permit a free passage for clean 
ing and repairs. 
f t Water space between the flues. 
cj, Steam box, on which are fitted the 
safety valves g in close iron boxes y". 
h, Is the stop valve, fitted on the 
upper end of the steam pipe ti, so 
that the steam may be completely 
shut off from either boiler, and the 
engines, as found necessary. 
B, The steam cylinder, with its piston 
B'; m, m, m, steam slide casing, of 
which the boxes m,m\ contain the 
steam slides wdiich are connected by 
the pipe m', with the steam pipe h\ 
leading from the boiler A. 
n, n, n", Exhaustion slide casing, the 
boxes n, n, containing the exhaus 
tion slides, which are connected 
with the top chamber of the con 
denser L, by the exhaustion pipe n. 
and the nozle at n. 
Both the steam and exhaustion slide casings are cast on the cylinders, due con 
sideration being paid to the difference in expansion and contraction of the side pipes 
m, n\ and of the cylinder B. 
By this construction, the usual joints at the nozles, 1, 2, 3, 4, by which the slide 
casings are attached to the cylinders are dispensed with, and of course the risk of 
leakage avoided. 
r r, 5 s, Are the steam slide facings or back plates, through which are apertures 
corresponding with those of the nozles 1 and 2.