SEAHAM NO. 2 COLLIERY. 279 



takes place in that instead of in the bottom. A Little Hardy 

 coal cutter worked by compressed air is used for the headings 

 and narrow places ; for the rest, pick work is used. 



Compressed air is used, not only for the coal punchers, 

 but also for the pumps. A Norwalk straight line compound 

 air compressor is the type employed, driven by a single 20in. 

 diam. steam cylinder, the air cylinders being 17J and 24in. 

 diameter (Fig. 181). The steam and air cylinders being in 

 the same straight line, there are none of the cross-strains that 

 duplex compressors are subject to. The air is compressed to 

 901b. per square inch, and the capacity of the machine is 

 1650 cubic feet per air per minute. The air valves have a 

 positive movement , and are of the Corliss pattern. The speed 

 at which the air compressor works is determined by the con- 

 sumption of the air, a uniform pressure being maintained in 



Fig. 181. Norwalk compound straight line compressor. 



the air receiver. This is done by means of an automatic regu- 

 lator, which shuts off or admits steam according to the pres- 

 sure of the air. The air pipes are spiral riveted, Gin. in 

 diameter, made by Messrs. Mephan, Ferguson, of Footscray, 

 Vic. There are two small air receivers below, one on either 

 side of the shaft. 



The main pump, located at the bottom of the down-cast 

 shaft, is one of Evans' direct acting ram pumps, designed to 

 raise 10,000 gallons per hour. The cylinders are 20in. diameter, 

 the stoke 24in., and the rams, which are arranged horizontally, 

 are Tin. diameter. 



A Waddle fan, 35ft. in diameter, induces the necessary air 

 current. It has ten long vanes and ten shorter ones, all of 

 which are curved. This class of fan is peculiarly free from 



