482 On the Construction of Kitchen 



tion of steam, are kept constantly about half full of 

 water, which water they receive, already hot, from the 

 two upper cylinders, in which last the water should 

 never boil. 



These upper cylinders communicate, by an open 

 pipe, with a reservoir of water, which is situated several 

 feet above them ; consequently, as fast as they furnish 

 water to the four cylinders which lie below them, that 

 water so furnished is immediately replaced by water 

 which comes from the reservoir above. 



As the pipe which brings this water from the reser- 

 voir enters the cylinders some considerable distance 

 below their centres, and as the pipes which convey the 

 water from them to the cylinders below are fixed in 

 their centres, as cold water is heavier than warm water, 

 it is evident that the water which enters them cold 

 from the reservoir will take its place at the lower parts 

 of these cylinders, while only the lighter hot water will 

 be furnished to the cylindrical boilers below. 



The method of regulating the admission of water 

 into the boilers below, where the steam is generated, is 

 so well known that it would be superfluous to give a 

 particular account of it. 



In the set of boilers that has been put up at the 

 house of the Royal Institution, the open ends of all the 

 cylinders are on one side ; that is to say, they all come 

 through the front w r all of the brick-work. This arrange- 

 ment was rendered necessary in that particular case 

 by local circumstances : it would, however, have been 

 better if only the lower and upper pairs of cylinders had 

 come through the front wall, and the open ends of the 

 middle pair had passed through the back wall ; for 

 in that case it would have been easier to provide a 



