390 Intelligence and Miscellaneous Articles. 



being thus heated, and allowed to flow out at a given velocity, a 

 uniform flow of heat was obtained. 



Now, for the purposes of measuring this flow of heat, in the in- 

 stance of a gas-meter, the source of heat is present by the inflam- 

 mable gas itself ; and, after numerous experiments, it was fully and 

 conclusively ascertained that a jet of gas, issuing out of an orifice, 

 perforated in the side of a small solid brass cylinder (such as will be 

 afterwards described, and shown in the annexed figures), will heat 

 the said cylinder to a uniform given temperature, whatever be the 

 height of the said jet : for, with a small flame, the jet clings, as it 

 were, and is in immediate contact with the solid cylinder ; whereas, 

 when the flame issues from the orifice with considerable velocity, still 

 the longer jet only imparts the same degree of heat to the solid cylinder 

 as did the smaller one ; the'increased (or lengthened) flame being, in 

 this latter case, driven away from any closer contact by its own ve- 

 locity, or rather by the velocity due to the pressure of the gas issuing 

 from the orifice. This fact having been thoroughly established by 

 repeated experiments and practice, the necessary apparatus of the gas- 

 meter, for the practical application of the fact, became very simple. 



The next point expedient to be determined accurately, was the 

 proper superficies of a receptacle, to be heated by or from such a solid 

 cylinder as the one just described ; which surface would be sufficient 

 to communicate the requisite heat to such portion of the whole quan- 

 tity of gas to be measured, as it was necessary to pass through the 

 receptacle, without altering the temperature thereof in any percep- 

 tible degree. This point was ascertained, as the preceding ones 

 were, by repeated experiments ; and, further, it was found advisable 

 that the receptacle for heating the gas should be well clothed with 

 the best non-conducting substance, to keep it at a proper tempera- 

 ture. The proportionate surface of the receptacle having been de- 

 termined, certain other proportions and dimensions were established, 

 which, as applicable to a six-light meter, are given in the figures 

 accompanying the subsequent mechanical description. 



Lastly, it remained to be found what quantity of gas, heated in the 

 manner previously described, and discharged upon one of two such 

 glass cylinders as before mentioned, would be sufficient to expel the 

 alcohol therefrom, and drive it into the other cylinder. Numerous ex- 

 periments and long practice have determined this quantity to be no 

 more than about one- seventh part of the whole gas requisite to supply 

 the number of burners, the consumption whereof is to be measured. 



This being conclusively established, led to the consequent arrange- 

 ment of dividing the flow of gas as applied from the main, so as to 

 pass them separately through two openings, one of which should have 

 its area six times that of the other, whereby six-sevenths of the gas 

 admitted from the main might flow towards the burners without 

 passing through the working part of the meter, leaving the remaining, 

 or one seventh, part to perform the necessary functions of registering 

 the amount of the whole quantity. The simple manner in which 

 this arrangement is carried into effect, is duly pointed out by the 

 figures, and is described in the subsequent explanation of the whole 

 of the mechanical contrivances for the proper working of the meter. 



