122 An Essay on Rents. (Fes. 
the air, but principally by change of quantity, from the diminished 
supply of the retarded current. The flame is extinguished principally 
in consequence of atmospheric air being excluded from all access to 
it, by the entering gases. The flame is not extinguished until the 
gases arrive at and are fired by it; and if they be explodible, they 
will explode, and communicate with the gases without. 
The only remaining plan indicated is that conformably to which 
the accompanying lantern has been constructed, to exclude all com- 
munication of the flame from the air within which the lantern is 
placed, and to derive its supply of air from the floor of the mine, 
from that stratum into which the alarmed miner depresses his taper, 
which if it be of azote and carbonic acid gases, or choak-damp, 
will only extinguish his light, and only in the last supposeable ex- 
tremity of a mine filled to the bottom with fire-damp, will produce 
explosions, could any person be supposed capable of existing in 
such a mixture of carbureted hydrogen gas, or of -persisting to ad- 
vance into it, notwithstanding the various other notices he would 
have received of his danger. 
This evil results from the consideration of these expedients. Up- 
air shafts are neglected, and a due course of mining, whilst the 
result is awaited of contrivances which, after all, can only be 
auxiliary to those, and are injurious, as they tend to supersede their 
use, and prevent their establishment. In the west I understand 
that collieries are opened and conducted upon principles which dis- 
charge all accumulations of light gas by upward drainage, and pre- 
vent all descent of waters below their drainage level from the surface 
of the earth. Conformably to these principles, as far as may he, 
the mines in the north should be improved, opened, and conducted 
in all their future workings, 
ARTICLE X. 
An Essay on the Shapes, Dimensions, and Positions of the Spaces 
in the Earth which are called Rents, and the Arrangement of the 
Matter in them: with the Definition and Cause of Stratification. 
By Mr. John B. Longmire. 
(Concluded from vol, vi. p. 414.) 
On the Cause of Formations. 
I nave already gone through, in a brief way, those parts of my 
advertisement which relates to internal and surface rents, and to 
stratification ; and I have now only to show that the phenomenon 
of formations is an “ effect of the unequal contraction of the 
earth’s matter.” r 
In this essay I will adopt an arrangement, as consistent as I am 
able to make it, with the manner in which I conceive the visible 
