The workingman's advocate. [volume] (Chicago [Ill.]) 1864-1877, 1875-07-31
FROM ILLINOIS.

MrNo>k. Ills. July Is, 1873.
To the Ed.,raf .he waFsr>ax,>', ADVOCATE
Sir ia your issue " July 10th, |
notice a letter from NJ "A vt Fair Haven,
wherein he asserts the following Mr..
Mcdonald says, II It y not the atmos-
pheric pressure that causes the circulation
Of air in the shaft, pray where does the
force come from" tie cannot find such
words iu ny letter This willful misrep
sentatiou would imply that ! had said the
atmospheric pressure was alone the cause
Of the circulation ~ air II mines. Several
times have had occasion to correct similar
mistakes, but this one crowns them All.
In fact ! begin ID think that he has an in
herent weakness for such. so mnch so,
that If the facts IN any given iase are not
quite sufficient for his logical emergencies,
or for the qualification Of his vanity, he
will water them JUST TO raise an argument.
But to the point at issue, W II. says:
The atmospheric pressure has nothing to do
with causing the natural currents Of air in
mines While say, the atmospheric
pressure has a great deal To do with circu-
lation Of air in mines. To make a simple
illustration, let us suppose we have two
shafts sunk to depth Of one hundred
feet, having communication with each
other at the bottom, and that on top they
are both equally exposed to the atmos-
phere, then as 1t is the generally received
opinion, that the atmosphere is forty five
miles high, and has a pressure Of about
fifteen pounds to the square inch on the
earths surface, then it is evident that each
shaft will be filled to the brim, with the
atmosphere, and the pressure Of the same
will ~ equal in both shafts, to the furth-
est extremity of the mine, and, if there is
no natural heat in the mines there is
no circulation Of air, and before any cir
culatIon Of air can take place we have got
to diminish OF increase the atmospheric
weight or pressure in one Of the shafts re-
ferred 70. A common contriveLce for such
purpose Is the placing Of a furnace at the
bottom Of the upcast shaft, thus heating
the atmosphere in one of the shafts to a
higher temperature than the other will
diminish the weight OF pressure Of the at
mosphere, on the top Of the upcast shaft,
thereby giving the propeling force to the
downcast shaft, because Of the undimin
lshed atmospheric weight or pressure that
It still maintains Weight must be added
to or taken from The atmospheric pressure,
Gather by the natural heat in the mines OF
by some artificial contrivence, before a
circulation of air can take place, and no
matter what contrivence is applied for that
end the atmospheric pressure il the great
assistant, at least such is my opinion. w
II. started out to prove from nv letters
that | did not understand the nature "a
air. | must confess that l don't know II
all, but with &c years experience amonyst
the different gases that are incident Ia
mines, and having suffered more or les,
from the effects of each of the different
kinds Of gases, think l know little Of
their nature and effects, and how to cope
with them by the common modes of venti
latlon. But if w. III. can prove from my
letters that don't, he is at perfect liberty
to do so, or if he chooses, can give him a
better and wider field to work upon t.
further the landable object he has in view
by giving him the names of several shafts
that have sunk, opened and ventilated.
c. Med.