1816.] On the Ventilation of Coal-Mines. 289 
er lower edge, which shaft is 180 yards in depth. E is another 
shaft, distant 1200 yards from A, which is also sunk to the coal on 
its higher, or north-western, side. . If the coal be supposed to rise. 
from B to Dat the rate of one yard in twelve, then D must be 100, 
yards higher than B; consequently the depth of the shaft, E, from: 
the surface will be 80 yards. ; Te ciate ty 
It has already been observed that it is possible to'sink pits to these 
or to greater depths, without danger to the lives of the workmen. 
It is now to be added that it is also possible to open a communica~ 
tion below ground, between pits situated at considerable distances 
from each other; and that when two or more pits are sunk for one 
mine, the first operation is to open such a communication... - 
Let it be supposed, then, that a communication .between ‘the: 
shafts A and E has been opened in the usual way, by digging a 
passage through the.coal from B to D. The whole passage, A, B, 
C, D, E, will then resemble a tube, .of which-the two divisions, . 
A, B, and-E, D, are perpendicular to the horizon, and of which the 
middle part, B, C, D, has a considerable angle of declination 
from it.) 6 : pad ark eS eae 
It would seem to be evident, @ prior?, that a current of air, if it 
should move at all, without mechanical impulse, would proceed, in 
a tube of this form, and in this ‘position, from A to’, and not 
from Eto A; but this may easily be subjected to experiment. 
1. Let atube be constructed of any material which conducts heat . 
slowly, as glass, for instance... Let it be made exactly of the form 
represented in Fig. 1, and placed precisely in the same position 
with respect to the horizon. Let heat be applied to any part of the 
middle division, B, C, D, by the flame of a lamp, or otherwise, and 
a circulation of air will commence, and proceed from A. to. K;: 
which may be made evident by placing alittle down of feathers: 
over each opening of the tube: the ascending air will carry it 
upward from E, while the descending current will press it ‘downward 
into A. 2. Let the tube be filled with carbureted bydrogen gas, or 
fire-damp. ‘The same effects will follow, ‘without the application of, 
heat, or of any mechanical impulse, whatever. » Apply heat, as 
before, and it will increase the rapidity of the current. 3. Fill the: 
tube with any proportions, equal or unequal, of fire-damp and 
common air: the current will still take the same direction, aud will 
still be quickened by the application of heat. 
These are all the cases that can possibly occur, involving the 
chances of danger from inflammation, or explosion, in the passage 
A, B, C, D, E, considered as the first openings of a coal-mine ; for: 
this passage must either be filled with common air, with fire-damp, 
or with certain proportions of each with the other. But with 
whichever of these kinds or mixtures of air it.may be filled, it must 
circulate ; because, first, the temperature is known to be in general 
higher below ground than at the surtace, which would begin: the: 
circulation ; and, secondly, because B, being 100. yards ‘deeper: 
than D, would continue it in the direction C, D, E. : 
