NATUKAL HISTORY BUILDING 81 



being there discharged at an angle of 45° directly across the stack, 

 it becomes superheated by contact with the hot gases and passes to 

 the atmosphere generally invisible to the eye. The exhaust main 

 contains an automatic back pressure valve which automatically opens 

 in case the vacuum is lost and closes when the vacuum pumps are 

 started. At the point where the main rises from the trench a small 

 vacuum pump, 3^ by 5 by 5 inches in size, is located in a pit. Its 

 purpose is to remove the water of condensation which collects there, 

 and discharge it into a large blow-off tank behind the boilers. The 

 steam separators over the top of the engines, as well as all drips to 

 the main line, are connected through a system of pipes to a Holly 

 return device which returns the water of condensation to the boilers 

 automatically without the use of traps or pumps. In all other places 

 where water is liable to accumulate connection is also made to the 

 Holly system so that there is no likelihood of trouble through water 

 hammer. 



The boiler feed pumps, two in number and measuring 8 by 5 by 12 

 inches, are connected so that either can be run while the other is 

 undergoing repairs or held in reserve. Their speed is automatically 

 controll-ed through a regulator, which closes off steam from the 

 pump when the feed regulators on the boilers stop the passage of 

 water to the latter. There is a large feed-water heater composed 

 of a number of 1-inch horizontal copper tubes through which a part 

 of the exhaust passes, the condensation being removed by means of 

 a 6 by 8 by 12-inch vacuum pump. The water from the oil separator 

 passes to the heater to which the suction of the feed pump is con- 

 nected. A city Avater supply connection is also made to the tank 

 to replace what is lost between the engines and the oil separator. 



Handling of coal and ashes. — Bituminous coal is used in the fur- 

 naces, but with the type of stoker employed the amount of smoke 

 produced at any time is inappreciable. The coal requires to be 

 crushed and is delivered in that condition. 



Two coal bunkers have been provided. They are located at the 

 outer end of the east wing, one on each side of the inner wagon 

 drive the width of which was reduced to one-third its original di- 

 mension to subserve this purpose. The northern bunker, the floor of 

 Avhich is on the same level as that of the story, has a capacity of 

 about 350 tons. The southern bunker, whose floor level corresponds 

 v^^ith that of the driveway, has a capacity of some 475 tons and was 

 intended as a reserve storage. Its use for this purpose after a short 

 trial has, however, been at least temporarily abandoned since the one 

 bunker has been found to answer the requirements. 



The coal is handled mechanically, the machinery being located in 

 the northern bunker and operated by a 5 horse power motor. As it 

 80120°— Bull. 80—13 6 



