annular brick furnaces, etc., in which a uniformity of temperature in
the different chambers is of vital importance to perfect the baking. In
these furnaces the tube of the pyrometer is inserted through one of the
apertures at the top, as shown in Fig. 7. The dial is graduated up to
750 deg., which is more than sufficient, since the temperature of the upper
part of a compartment fully exposed to the heat rarely exceeds 670 deg. to
680 deg. C.

[Illustration: Fig. 7.--The Pyrometer mounted on a brick furnace.]

* * * * *




MANUFACTURERS' SOAPS AND THEIR PRODUCTION.

By W. J. MENZIES.


Potash soaps are generally superior to soda soaps for most purposes, but
more especially in washing wool and woolen goods. The difference between
the use of a potash and a soda soap for these purposes is very marked.
Potash lubricates the fiber of the wool, renders it soft and silky, and
to a certain extent bleaches it; soda, on the other hand, has a tendency
to turn wool a yellow color, and renders the fiber hard and brittle.
It cannot be too strongly insisted upon, therefore, that nothing but a
potash soap (or some form of potash in preference to soda if an alkali
alone is employed) should be used in washing wool in any form--either
manufactured or unmanufactured. This is fully borne out by nature,