GASOMETERS. 



131 



The standards S, eight in number, are each formed of three cast-iron frames, 

 six feet broad at their bases, of the same height as the gasometer, and 

 jointed together in the form of a T on the plan ; they are secured to the 

 stone (marked in the engraving) by dovetailed lock-nuts, keyed and 

 leaded, as represented in the figure. 



Fig. 30. 



Preference is often given to rollers, instead of rings, for guiding the rise of 

 the gasometer, and perhaps as there is less friction they may be more advan- 

 tageous ; their only inconvenience is the liability of their coming out of the 

 guides. I have shown a roller in the cut which works against the flanch of 

 the centre standard, widened for that purpose. 



H is the wooden curb, which ought always to be attached to a gasometer ; its 

 use is to regulate the flow of gas from one gasometer to another. While 

 immersed in the water of the tank it acts as a float, and, to some extent, 

 buoys up the vessel ; when the gasometer has risen to its full height, it acts 

 as a weight, being partly out of the water, thus causing the gas to flow 



s2 



