UPON SOME OF THE PHENOMENA OF COIUBUSTION. 
II. At a pressure of 30'4 inches, fuse No. 2 burnt 30 seconds. 
III. At a pressure of 30’4 inches, fuse No. 3 burnt 30 seconds. 
IV. At the mean pressure of 28*4 inches, fuse No 4 burnt 32 seconds. 
V. At the mean pressure of 28-1 inches, fuse No. 5 burnt 32-5 seconds. 
VI. At the mean pressure of 25-55 inches, fuse No. 6 burnt 35 seconds. 
VII. At the mean pressure of 25-85 inches, fuse No. 7 burnt 34-5 seconds. 
VIII. At the mean pressure of 22-35 inches, fuse No. 8 burnt 38 seconds. 
IX. At the mean pressure of 22-55 inches, fuse No. 9 burnt 37-5 seconds. 
X. At the mean pressure of 19-9 inches, fuse No. 10 burnt 42 seconds. 
XL At the mean pressure of 19-4 inches, fuse No. 11 burnt 41 seconds. 
XII. At the mean pressure of 16-15 inches, fuse No. 12 burnt 46 seconds. 
XIII. At the mean pressure of 15-75 inches, fuse No. 13 burnt 45 seconds. 
633 
It will be seen, from an inspection of the above numbers, that, after the three first 
experiments at atmospheric pressure, an attempt was made to burn two fuses at the 
same pressure, but owing to the gauge sinking to the extent of about two inches dui’ing 
the deflagration, the mean pressures at which each pair of fuses were burnt never 
exactly coincided. For the purpose of comparison, however, it will be convenient to 
take the mean both of the pressures and times of burning of each pair, and to express 
the results as follow : — 
Average pressure, 
in inches of mercury. 
Average time of 
deflagration of 6-inch 
fuse. 
Increase of time of 
burning over pre- 
ceding observation. 
Eeduction of pressure 
corresponding -with 
increase of time. 
Increase of time for 
each diminution of 
1 inch pressure. 
seconds. 
seconds. 
inches. 
seconds. 
30-40 
30-33 
28-25 
32-25 
1-92 
2-15 
-893 
25-70 
34-75 
2-50 
2-55 
•980 
22-45 
37-75 
3-00 
3-25 
•925 
19-G5 
41-50 
3-75 
2-80 
1-339 
15-95 
45 50 
4-00 
3-70 
1-081 
There are here e\ident indications of the rate of retardation being somewhat greater 
at low than at comparatively high pressures; but, neglecting these indications, the 
above numbers give 1-043 second as the average retardation in a six-inch or thirty- 
seconds fuse for each inch of mercurial pressure removed. This result agrees closely with 
that obtained by Quartermaster Mitchell, if we except those fuses which he burnt at the 
greatest altitude, and in referenee to which some error must obviously have crept in, 
either as regards the altitude of the station where the fuses were burnt, or the duration 
of _^their combustion. The latter source of en’or is perhaps rendered less improbable, 
from the fact that only two experiments were made at the greatest altitude, whilst six 
were performed at two, and four at the third of the remaining stations. The following 
Table shows Mr. Mitchell’s results, uniformly with those in the last Table. The fuses 
which he employed being fifteen-seconds or three-inch ones, I have multiplied their 
