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EXPLANATION OF THE PLATES, 



PLATES XLIX. AND L. 



ENGINES OF HER MAJESTY'S STEAM SHIP MEG^ERA. 



Her Majesty's steam ship Megeera 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 

 , 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, Water space between the flues. 

 9, Steam box, on which are fitted the 

 safety valves g in close iron boxes g". 



h, Is the stop valve, fitted on the 

 upper end of the steam pipe //, 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 which are connected by 

 the pipe m', with the steam pipe h, 

 leading from the boiler A. 



n, ri, 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 ri, 

 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, ri, 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, s s, Are the steam slide facings or back plates, through which are apertures 

 corresponding with those of the nozles 1 and 2. 



