24 KEPORT OF COMMISSIONER OF FISH AND FISHERIES [22] 



Length of the 15, 12, and 11-incli flues feet.. 10 



Length of the 9-inch flues - do.. 164 



Diameter of the complete chimney inches.. 52 



Height of the chimney above the grates feet.. 46 



Aggregate area, for draught, over the bridge- wall in both boilers, in 



square feet 18.16 



Aggregate area through the lower flues of both boilers square feet . . 13.962 



Aggregate area through the back connections for draught in both boil- 

 ers square feet . . 26.791 



Aggregate area through the upper flues of both boilers do 14.157 



Cross-area of smoke-pipe do 14.700 



Aggregate heating surface in the furnaces of both boilers do 224 



Aggregate heating surface in the lower flues of both boilers do 440.836 



Aggregate heating surface in the upper flues of both boilers do . .^. . 1,281,614 



Aggregate heating surface in the combustion chambers of both boil- 

 ers square feet . . 116 



Aggregate heating surface in the back connections of both boilers, square 



feet 304 



Aggregate heating surface in the front connections of both boilers, square 



feet 112 



Total water-heating surface in both boilers square feet . . 2, 478.5 



Total superheating surface in both boilers do 204 



Ratio of grate to cross-area over bridge-walls 5.429:1 



Ratio of grate to cross-area through lower flues 6.828:1 



Ratio of grate to cross-area through back connection 3.558:1 



Ratio of grate to cross-area through upper flues 6.743:1 



Ratio of grate to cross-area through chimney 6.485:1 



Ratio of water-heating surface to grate-surface 26:1 



Height of the center of the steam-pipe opening above the normal level of 



the water in the boilers feet.. 11.5 



The weights iu the boilers are distributed as follow : 



Ponnds. 



Wrought-iron and steel in the shells of both boilers 62, 971 



The flues in both boilers , 18,425 



Braces in both boilers 10,420 



Rivets, socket-bolts, manhole plates, &c 14, 618 



Safety-valves, stops, checks, ash-pans, and floor-plates 14, S94 



Smoke-pipe, cape, and casing 3, 599 



Weight of water in both boilers 69, 197 



There are two screw-propellers, one right and one left, of cast iron, 

 the blades curving backward, the edges curved, the forward or lead- 

 ing corner being curved to a radius of 17 inches, and the trailing cor- 

 ners curved to a radius of 16 inches. The length of the blades, on the 

 line of the axis of the screws, is from 23 to 26 inches. The principal 

 dimensions are as follow: 



Diameter feet.. 9 



Greatest diameter of the hub inches.. 17^ 



Fitch (uniform) feet.. 14^ 



Number of blades, each 4 



Fraction of the pitch used, from 0.2696 to 0.5898 



Helicoidal area of each screw square feet.. 42.02 



Thickness of blades at fillet of hub inches.. 4i 



Thickness of blades at periphery do f 



Weight of each screw pounds.. 4,038 



