a. The explosion tube was longer and wider.
b. The interrupters or " bridges " were of silver foil, and no fulminate was used.
c. A longer space was allowed between the firing spark and the first "bridge" where the record of the rate was begun. This was found essential in several cases, especially when the mixture was fired under reduced pressure, or in presence of inert gases, in which cases the explosion does not reach its maximum rate for some feet. per second.
§ 3. On the Constant Velocity of the Explosion Wave.
Experiments on the rate of explosion of hydrogen and oxygen in a leaden tube, 55 metres long and 8 mm. in internal diameter, gave a mean rate of 2817 metres In a tube of the same diameter and 100 metres long, the mean rate was 2821 metres; and in a tube 100 metres long and 13 mm. diameter the mean rate was 2819.
The general mean of these experiments--viz., 2819, is in close agreement with the mean result obtained by BERTHELOT in a shorter tube.--viz., 2810.
The constancy of the rate of the explosion-wave, under ordinary conditions of temperature and pressure, was, therefore, fully confirmed.
In the course of this investigation I have made many measurements of the rate of explosion of hydrogen and oxygen under ordinary corditions. Some of these were made with more precautions than others, so that in arriving at the most probable value of the rate, I have given greater weight to some sets than to others. The sets, each of which consists of from eight to ten distinct measurements, are lettered in the following table A, B, C, etc., in the order in which they were made :-
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TABLE V.-General Mean of H, + O Rates. Date. Sets. Mean. 1884, 1885 1888 1889 1890 A + B +C D E + F + G H 2819 2822 2824 2818 2821 The details of these experiments will be found in the Appendix.
§ 4. The Influence of Pressure on the Velocity of the Explosion Wave.
Preliminary experiments on the rate of explosion of hydrogen and cxygen under 500 mm. and 1000 mm. pressure having shown an appreciable difference, careful
