90 DISCOVERY REPORTS 



The cylinders of the main engines are i8, 28|, and 48^ in. diameter respectively, 

 having a common stroke of 28 in. The main engines are designed to develop about 

 1250 H.p. at 128 revolutions per minute. There are no pumps worked off the main 

 engines, all pumps being independent. The strength of all shafting is well in excess of 

 Lloyds' requirements, to ensure, so far as practicable, immunity from damage when 

 encountering ice ; this has already proved advantageous. The reversing gear is of Brown's 

 make, direct-acting hand and steam type. An independent surface condenser is fitted 

 with ample cooling surface to ensure a good vacuum in tropical waters when required. 

 This condenser is constructed of mild steel and is of Messrs Weir's regenerative type. 



An independent air pump of Messrs Weir's monotype, and a Weir's vacuum aug- 

 mentor are fitted, the latter being intended for use more particularly when the vessel is 

 passing through tropical waters. An independent auxiliary air pump is also fitted for 

 harbour service. The circulating pump is of the centrifugal type and two independent 

 engines are fitted, either of which has ample power for driving the pump. 



The propeller shaft is of steel throughout, no liners being fitted, and the stern tube is 

 provided with the builder's type of "Newark" oil-retaining device, enabling the shaft 

 to be run in oil in white metal bushes. This arrangement has proved satisfactory; no 

 rebushing has yet been carried out and the wear-down in the bushes has been found to 

 be negligible. A steam coil is fitted round the stern tube for thawing purposes when low 

 temperatures are encountered. The thrust block is of the single-collar Michell type 

 having specially large surface. 



The propeller is of the built type. It has a cast steel boss and four portable high- 

 tensile bronze blades, the blades being of Messrs Stones' make, machined to pitch and 

 specially strengthened for contact with ice. 



The two feed pumps are of Messrs Weir's make with float regulators: either is 

 capable of supplying the boilers at full power. A large general service pump is fitted 

 for dealing with reserve feed water and other services, and this pump is also avail- 

 able for circulating the main condenser if required. A small general service pump 

 is also provided for dealing with the sanitary service, wash deck and similar arrange- 

 ments. An independent Duplex pump is fitted for dealing with the fresh-water service 

 only. The evaporator and distiller are of Messrs Kircaldy's make, the evaporator having 

 a capacity of 15 tons per 24 hours and the distiller capable of producing 10 tons of fresh 

 water per 24 hours. The feed filter is of the gravity type with float control to Weir's 

 pumps. A feed heater is also fitted, using the exhaust from the auxiliary machinery. 



Lifting gear is provided in the engine room, together with large tanks for the storage 

 of lubricating oil. 



The boilers are two in number and of the ordinary cylindrical horizontal return-tube 

 type. They have a working pressure of 200 lb. to the square inch. The diameter of the 

 boilers is 13 ft. and their length is 11 ft., the total combined heating surface in both 

 boilers being 3550 square ft. The furnaces are of Deighton's corrugated-section with- 

 drawable type. Boiler mountings throughout are of gun-metal and of Messrs Dew- 

 rance's well-known make. 



