274 Dr Andrew Fyfe on the Comparalive Value of 



On viewing the results above given, it will be observed, that 

 the times for the consumpt of 1 foot are very nearly the same. 

 Had the difference followed any regular gi^adation, then we 

 might have supposed that it was occasioned by the difference 

 in the size of the aperture in the jet ; but as it does not do so, 

 we may, I think, safelyconclude,that,withjetsof different aper- 

 tures, and with flames of the same height, the quantity of the 

 same gas consumed in the same way is the same ; or that the 

 times for equal consumpts are the same. That this is really 

 the case is still farther proved by taking a small jet of gas, 

 of given height of flame, and marking the consumpt by meti^e ; 

 then removing the jet from the socket, which is left open, and 

 consuming the gas from it ; the quantity, in the same time, 

 will be found to be the same. Or, burn the gas from the latter, 

 with a flame of such a height as can be measured with any 

 degree of accuracy ; then introduce a jet, and burn the gas 

 with the same height of flame ; the quantities consumed are 

 the same, or as nearly so as can be expected from trials of 

 the kind, where it is difficult to measure accurately the length 

 of flame. Hence, most probably, the cause of the difference 

 of time in the table given ; that difference having been occa- 

 sioned by the flame in some of the trials having been a very 

 little too high or too low, in the cases where the difference 

 is greatest. Even that diflFerence, especially in the last 

 table, the experiments of which were repeated again and 

 again, with slightly varying results, is only 1' 20". This 

 shews the necessity of i-epeated trials, altering the flame, and 

 again bringing it to the fixed height, and each time mark- 

 ing the consumpt and the pressure, so that, by taking the 

 average of many trials, an accurate result may be obtained. 

 Having fixed on the jet 40, bushed with platinum, and fur- 

 nished with the scale for the flame, and with the pressure- 

 gauge, I found, by numerous trials, that the time for the con- 

 sumpt of 1 foot of a gas, was 64' 41", the flame being 5 inches. 

 The pressure at the burner-gauge was i J^ths. The specific 

 gravity of the gas was, by experiment in the usual way, 

 found to be 602 6, at 60°, and barometer 30 ; of course one 

 foot requiring 64' 41", then in 60', there are consumed 0-927 of 

 foot. Thus, then, the consumpts being, in equal times, as the 



