e current of
blast passing through the spiral heater.

The method of graduating the indicator scales of the Frew pyrometer is
worthy of special notice. When the apparatus is fitted up, and before it
is permanently fixed in position, the spiral heater is placed in cold
water of known temperature, and the point noted at which the colored
liquid stands in the indicator tube. The water is then boiled, and the
rise in the liquid in the tube is again noted. Suppose, in the first
instance, the cold water temperature to be 62 deg. Fahr., and that, from
this point up to 212 deg. Fahr., the liquid to have risen 21/4 in. in the
tube; this is equal to 11/2 in. per 100 deg. Fahr., and from these data a
scale is constructed, the correctness of which is easily verified by
transferring the spiral heater into an air bath or oil of high boiling
point, and then comparing the readings of the pyrometer scale with those
of a mercurial thermometer placed alongside of the spiral heater. By this
means it can be clearly demonstrated that, up to the highest point to
which it is safe to use a mercurial thermometer, the readings of the
pyrometer scale and that of the thermometer are identical.

While this pyrometer is particularly valuable for indicating the
temperature of hot blast stoves of every description, there are doubtless
many uses that will suggest themselves to persons engaged in various
industrial arts and manufactures. The apparatus is neat and substantial
in its parts, while it occupies very little space, is not at all liable
to derangement, and is entirely automatic in its action. A number of the
instruments have been in continuous use at the Langloan Iron Works, with
the most satisfactory results, for about eight months. The temperatures
they are graduated for vary according to the furnaces with which they are
connected and the kind of work to which these are
applied.--_Engineering_.

* * * * *

An exchange gives the following very simple way of avoiding the
disagreeable smoke and gas which always pours into the room when a fire
is lit in a stove, heater, or fireplace on a damp day: Put in the wood
and coal as usual; but before lighting them, ignite a handful of paper or
shavings placed on top of the coal. This produces a current of hot air in
the chimney, which draws up the smoke and gas at once.

* * * * *

[FROM PHOTOGRAPHISCHE CORRESPONDENZ.]

ORTH