394? Intelligence and Miscellaneous Articles. 



From the preceding, it is clearly proved that the illuminating 

 power of gas depends upon the quantity of oxygen consumed, and 

 of carbonic acid produced during combustion. 



The object of Dr. Henry's paper was only to prove the illuminating 

 power of the gas ; in order therefore to prove that the heat from 

 the combustion of any gas increases in the direct ratio of the oxygen 

 consumed, the following is extracted from Professor Graham's Trea- 

 tise on Chemistry : — 



" From the late researches of Despretz and of Bull, a very inter- 

 esting rule has been obtained ; it is as follows : — ' That in all cases 

 of combustion the quantity of heat evolved is proportional to the 

 quantity of oxygen which enters into combination.' " 



And in Henry's Chemistry, ninth edition, p. 422, we find it stated, 

 that " by the combustion of denser gases, a higher temperature is 

 produced." See also Williams on Combustion. 



The heat and light from the gas having been thus demonstrated to 

 be proportionate to each other, we have, in the preceding apparatus, 

 a meter which will measure the quantity of light given forth, which 

 is the real end to be desired, and the following description of the 

 mechanical arrangements may be now proceeded with. 



Figures 1, 2, 3 represent different parts and positions of " Clegg's 

 Patent Differential Dry Gas-light Meter." They are drawn to 

 a scale of 3-10ths of an inch to one inch, or in that proportion to 

 a full-sized meter, capable of measuring the consumption by six large 

 gas-light burners, that is a " six-light meter." The same letters refer 

 to the same parts in all the figures. 



A A A is a cylindrical cast iron vessel, being the case of the meter 

 of about a quarter of an inch thickness of metal (made thicker at 

 particular parts requiring it), and five inches outside diameter. P P 

 are hoods or projections, parts of the same casting of the entire case 

 or vessel, the important functions of which have been previously 

 explained. The references to the working parts, distinguished by 

 the other letters, will be made in the subsequent explanations. 



For the sake of distinctness and simplicity of description, it may 

 be best to show, first, the manner in which the gas flows through 

 the vessel, and the action of all those parts which are essential to 

 the mere meter, taking up afterwards certain auxiliary mechanical 

 contrivances, quite independent of the general principles on which 

 the meter is constructed, or of the actual operation of registering 

 the light, these contrivances being chiefly introduced for preventing 

 frauds. 



When the gas is first turned on at the main stop-cock, it flows into 

 the meter through the openings or pipes, M, to the valve O, which 

 opens into a vertical passage at the back of the meter. Along the 

 upper part, H, of this passage flows a small portion only (viz. one- 

 seventh of the whole), gas finding its way into a receptacle called 

 the " heater," into which it enters through the pipe at I, and thence 

 fills every part of the main body of the meter, where the working 

 parts are disposed ; the direction of this flow or current of gas is in- 

 dicated by short light arrows along its entire course. The remaining 



