This compound is impervious to water, so the negative print is
removed by simply washing with a damp sponge, the same as removing
writing from a slate. This makes it possible to place another
original on the pad immediately without waiting for the ink to
vanish by chemical action as in the original hectograph.
The action of the weather has no effect upon this compound and it
is proof against accident, for the tray may be dropped and the pad
dented or cut into pieces, and the clay can be pressed back and
leveled. The only caution is to keep it covered with a cloth
saturated in glycerine while not in use.
--Contributed by A. A. Houghton, Northville, Mich.
** Paper-Clip Bookmark [241]
The combination of a paper clip and a calling card makes a good
bookmark.
[Illustration: Bookmark]
The clip and card can be kept together by piercing the card and
bending the ends of the wire to stick through the holes. The clip
is attached to a page as shown in the sketch.
--Contributed by Thos. DeLoof, Grand Rapids, Mich.
** Aerating Water in a Small Tank [241]
A simple way of producing air pressure sufficient to aerate water
is by the use of a siphon as shown in Fig.
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