68 WATER IN MURIATIC ACIt> GAS? 



Improved addition of a pipe H, fig. 2, which is cast at the same time with 

 sinking of tne barrel, and communicates with it both at the top and at the 

 \vells, mine- bottom, just above the clack ; at the upper end the pipe is covcr- 

 ' * ed by a fl.it sliding plate, which can be moved by a small rod, b, 

 passing through a collar of leather ; the rod has a communi- 

 cation by a lever, so that the valve can be opened or shut by 

 the men in the bottom of the pit ; the object of this side pipe 

 is to let down such a proportion of the water, which the 

 pump draws, as will prevent the pump drawing air ; though of 

 course the motion of the engine will be so adapted, as not to 

 f require a great proportion of the water to be thus returned 

 through the side pipe j yet it will not be possible to work the 

 engine so correctly, as not to draw some air, without this con- 

 trivance j and if it does, it draws up much dirt and pieces of 

 stone into the pump, besides causing the engine to work very 

 irregularly, in consequence of partially losing its load every 

 time the air enters the pump. Another use of the side pipe is, 

 to let down water into the chamber of the clack to fill it, when 

 the engine is first set to work, after the pumps have been 

 standing still, and the lower part of the barrel and chamber 

 empty*. 



XV. 



An Account of an Experiment made in the College Laboratory , 

 Edinburgh, drawn up by Joijn Davy, Esq. 



SIR, 



If water be 1F"N the preceding numbers of your Journal, several papers have 

 the conTbiuZ "^" a PP^ ared > relative to the result of the combination of 

 nation of mur. muriatic acid and ammonia. Mr. Murray first made the expe- 



a. gas, and riment, for the purpose of ascertaining the nature of the 

 anim. gas, the ' ~ * * & 



viur.a.gas former gas — whether it be a compound of an unknown basis 

 contains none. anc j wa t er> or a compound of chlorine and hydrogene. He 



* This communication was accompanied by a handsome letter from 

 that eminent civil engineer, William Jessop, Esq., who, after explaining 

 the usual practice and the effect of Mr. Bruntons improvement, adds, 

 that simple as it is, it will be found, as he has from experience ascer- 

 tained, to be of considerable value to those interested in mining con- 

 cerns. 



justly 



