19 



the Dome, and along the roof ore 

 the Elgin Gallery. 



This main has connected with it six 

 stationary Engines which pump the 

 water into it from cisterns underneath 

 the roof, and these cisterns are in 

 their turn supplied by rising mains 

 connected with the external under- 

 ground pipe, and by that means also 

 connected with the New Eiver Com- 

 pany's Works. Although the water of 

 the New River Company is always on 

 sufficiently to keep the outside under- 

 ground tank aud pipes charged, the 

 pressure is not at all times sufficient 

 to drive the water into the cisterns 

 underneath the roof. At some period, 

 however, during every twenty-four 

 hours the pressure is on for a sufficient 

 time to fill all these cisterns which 

 may require water, the supply being 

 regulated by ball-cocks ; so that in all 

 ordinary circumstances they may be 

 calculated on as containing a full 

 supply of water up to the level at 

 which the balls close the cocks. 



In addition to the six stationary 

 Engines already mentioned, this 

 main has connected with it 36 Fire 

 Cocks and 9 Stop Cocks, the whole 

 being numbered consecutively from 

 50 to 94, both inclusive. All these 

 Stop Cocks, except the Cock marked 

 49 on S.W. Staircase, are ordinarily 

 kept open ; but any one or more of 

 them can be shut in case of need, so 

 that, if required, the whole of the 

 Engines can be worked together 

 through one or more Fire Cocks. 



The Hose pipes, the branches or 

 directing pipes and other necessary 



B 2 



