The Description of a Safety Fuinace. 211 
principle called gravitation, by which, false analogies have been 
introduced into philosophy.” Let us, however, in a single in- 
stance observe how these “ known motions of Nature” supply 
the place of the “ asswmed principle called gravitation,” _ 
The weight of bodies, and their velocity in falling, uniform 
experience shows to be least at the equator, and to increase 
with the latitude. Now as the rotary motion of the earth’s sur- 
face and atmosphere diminishes from the equator to the poles, 
where it ceases in both; the weight of bodies and their velocity 
in falling, ought, according to Sir Richard’s doctrine, to be 
greatest al the equator, and to diminish as the latitude increases. 
Nay further, since there exists neither rotary motion on the earth’s 
surface at the poles, nor in the atmosphere in its prolonged axis, 
a direct consequence of his doctrine is, that Lodies at the poles 
are devoid of all weight, and when projected perpendicularly 
thence, they never return to the earth! 
I am, sir, 
Your very obedient servant, 
Bath, Sept. 9, 1817. Fics 
XXXIV. The Description of a Safety Furnace for preventing 
_ Explosions in Coal-Mines. By Ropert BakEwELL, Esq. 
To Mr. Tilloch. 
Dear Sir,— [ue attention of coal proprietors has lately been 
directed to the explosions which take place in mines from the 
lights used by the workmen; but it is well known that similar 
explosions are often occasioned by the inflammation of the car- 
buretted hydrogen gas, as it passes the fire placed near the upcast 
shaft to rarefy the air and promote ventilation. The fire which 
is generally necessary, is thus not unfrequently the cause of the 
most fatal accidents, 
To prevent this, no remedy has been proposed that I am ac- 
quainted with, except the substitution of a charcoal fire, on the 
principle that the gas will not explode by a red heat burning 
without fame. An open charcoal fire is, however, liable to the 
following objections. The carbonic acid gas generated by the 
combustion of charcoal being specifically heavier than the air of 
the mine, will, as it is cooled in its passage upwards, descend 
again and choak the lower part of the shaft. A particle of com- 
mon coal intermixed with the charcoal, or falling into the fire, 
might produce flame and cause an explosion. The comparative 
dearness of charcoal will also tend to prevent its introduction. 
Coke from coal is more easily procured, but it sometimes beams 
02 
with 
