| hydrogen in | . . . | 3′·7, | the olefiant | gas in | 2′·75 |
| the second in | . . . | 3′·5 | „ | „ | 2′·5 |
| the smaller in | . . . | 3′·45 | „ | „ | 2′·8; |
and in several other experiments there seemed to be nearly an equal effect, when the quantity of gas passed in the same time was the same.
I imagined that the specific gravity of the gases might have some constant influence, but this does not seem to be the case; carbonic oxide and olefiant gas are nearly of the same density; and if the effect depended upon their weight, it should be nearly the same for both of them; but this is not so; seven cubical inches of carbonic oxide required 4·6 minutes to pass through a tube which was traversed by the same quantity of olefiant gas under the same pressure in 3·3 minutes, each gas having been placed over caustic lime for some time previously; and oxygen required to pass through the same tube 5·45 minutes of time.
I placed three gauges in different parts of a tube, of such a size that it passed olefiant and hydrogen gas in nearly equal times; the gauges were very obedient to the pressure of the gas in the different parts of the tube, but I could not perceive any difference between the effect of the different gases.
Such are some of the circumstances which affect and produce this curious effect: that the velocity of gases in passing through tubes should be in some proportion to the pressure on them is nothing particular; but the singularity is, that the ratio for the same gas varies with the pressure, and that this variation differs in different gases; thus the one which passes with the greatest facility at low pressure, passes with the least at high pressure.
It may be deduced from the experiments at high pressures and on obstructions, that the fluidity of the gas has little or nothing to do in this case, for where it alone can have an influence, the indications are the same at all pressures, and the gas of least density passes in the shortest time; thus comparing hydrogen with olefiant gas, and considering its time I, the time of the latter will be in the experiments already mentioned, as 2·38, 2·42, 2·4, 2·57, 2·46, 2·57 ratios, which do not differ much from each other, though the times, pressure, obstructions, and quantities of gas used vary very considerably.
