THE GOVERNOR. 147 



its weight, equal to that of the water which it displaces ; and the density of 

 gas contained in it will vary as the immersion. By making the chain F of a 

 proper weight, it may be made to answer the purpose of a regulator of the 

 pressure. Let it be supposed, for example, that the vessel weighs 1000 Ibs., 

 and loses 100 Ibs. of that weight when immersed in the water, and that a por- 

 tion of the chain, equal in length to the height which the vessel rises, shall 

 weigh 50 Ibs., and the counterbalance weigh 950 Ibs., 



Ibs. 



Then, when the vessel is immersed, its effective weight is - 900 



To which must be added the portion of chain now acting, as increasing 



the weight of the vessel - 50 



The sum corresponds with the actual weight of the counterbalance - 950 



Again, let the vessel be elevated out of the water, its actual and effective 



weight then is - 1000 



To balance which is opposed the counterpoise - - - 950 



And the portion of the chain now removed to the other side of the 



pulley to counterpoise, and acting with it - - 50 



The sum corresponds with the actual weight of the vessel - - 1000 



The effects of the vessel and counterpoise being thus opposed to each other, 

 the pressure of the gas contained therein is equalized. 



By adding or removing the weight of the counterbalance, an increase or 

 decrease of pressure may be effected. 



The action of the Governor is as follows. The outlet-pipe is connected with 

 the mains, and the inlet-pipe with the gasometer supplying gas into the ma- 

 chine : it will be evident, that if the density of the gas in the inlet-pipe becomes 

 by any means increased, a greater quantity of gas must pass between the sides 

 of the adjusting cone and the aperture in the plate d, the consequence of which 

 will be that the floating vessel will rise, and therefore contract the area of the 

 opening in d ; and if, on the contrary, the gas in the inlet-pipe decreases in 

 density, the vessel will descend ; so that whatever density the gas may at any 

 time assume in the gasometers or mains, its pressure in the floating vessel will 

 remain uniform, and consequently the velocity of the gas passing into the 

 mains will be regular: for when the aperture of the plate d would admit 

 more gas than necessary for the supply to the mains, the floating vessel rises 

 and diminishes the area of the inlet-pipe ; and when, on the contrary, the inlet 



u2 



