line, so as to protect the sides as well as the top from the action of
the acid; were this neglected, the acid would soon eat out the lines
from below. The greatest skill and care is, therefore, necessary in
this work, especially so in the case of some of the exquisitely fine
blocks which are etched for some art publications.

There are many details which are necessary to successful etching, but
those now given will be sufficient to convey to you generally the
method of making the zinc plate for the typographic block. After
etching there only remains the trimming of the zinc, a little touching
up, and mounting it on a block of mahogany or cherry of exact
thickness to render it type high, and it is now ready for insertion
with type in the printer's form. From a properly etched plate hundreds
of thousands of prints may be obtained, or it may be electrotyped or
stereotyped and multiplied indefinitely.--_G.S. Waterlow, Brit. Jour.
Photo._

* * * * *




ANALYSIS OF A HAND FIRE GRENADE.

By CHAS. CATLETT and R.C. PRICE.


The analyses of several of these "fire extinguishers" have been
published, showing that they are composed essentially of an aqueous
solution of one or more of the following bodies; sodium, potassium,