is not much heeded by heads of families or builders of houses. But in
any large community where gas comes into general use as an article of
fuel, this fact will gradually become recognized and respected.

The property of indicating the presence of very minute quantities of gas
in a room is claimed for an instrument recently described by C. Von Jahn
in the _Revue Industrielle_. This is a porous cup, inverted and closed
by a perforated rubber stopper. Through the perforation in the stopper
the interior of the cup is connected with a pressure gauge containing
colored water. It is claimed that the diffusion of gas through the
earthenware raises the level of the water in the gauge so delicately
that the presence of one-half of one per cent, of gas may be detected by
it. Other instruments of a slightly different character are credited by
their inventors with most sensitive power of indicating gas-leakages,
but their practical efficiency remains to be demonstrated. An automatic
cut-off for use outside of houses in which natural gas is consumed has
been invented, but this writer knows nothing of either its mode of
action or its effectiveness.

The great economic question, however, connected with the use of natural
gas is, how will it affect the industrial interests of the country?
There are grounds for the belief that a sufficient supply of natural gas
may be found in the vicinity of Pittsburg to reduce the cost of fuel to
such a degree as to make competition in the manufacture of iron, steel,
and glass, in any part of the country where coal must be used, out of
the question. Such a condition of affairs would probably result in
driving the great manufacturing concerns of the country into the region
where natural gas is to obtained. That may be anywhere from the western
slope of the Alleghanies to Lake Erie or to Lake Michigan. And, if the
cost of producing iron, steel, and glass can be so cheapened by the new