he following
cement is recommended by a scientific authority. It has the additional
advantage of being waterproof. Melt together equal parts of pitch and
gutta-percha. To nine parts of this add three parts of boiled oil, and
one-fifth part of litharge. Continue the heat with stirring until a
thorough union of the ingredients is effected. Apply the mixture hot or
somewhat cooled, and thinned with a small quantity of benzole or
turpentine oil.

A PORTABLE INK.

The aniline colors, which possess great tinctorial powers, can be
conveniently used in the preparation of a portable ink. Saturate white
tissue paper with an aniline violet, or with aniline black, by dipping the
sheets into a saturated alcoholic solution of these colors; then dry and
pack them in suitable parcels, and you will have a portable ink, either
violet or black.

INDELIBLE INDIA INK.

Draughtsmen are aware that lines drawn on paper with good India ink well
prepared cannot be washed out by mere sponging or washing. Now, however,
it is proposed to take advantage of the fact that glue or gelatine, when
mixed with bichromate of potassa, and exposed to the light, becomes
insoluble, and thus renders India ink, which always contains a little
gelatine, indelible. Reisenbichler, the discoverer, calls this kind of ink
"Harttusche," or "hard India ink." It is made by adding to the common
India ink of commerce about one per cent, in a very fine powder, of
bichromate of potash. This must be mixed with the ink in a dry state;
otherwise, it is said, the ink could not be easily ground in water. Those
who cannot provide themselves with ink prepared as above in a cake, can
use a dilute solution of bichromate of potash in rubbing up the ink. It
answers the same purpose, though the ink should be used thick, so that the
yellow salt will not spread.

TO MAKE COPYING INKS.

Dissolve in a pint and a half of writing ink (violet or any other color)
an ounce of lump sugar or sugar candy. A copying ink, so slow drying that
writing in it can be copied by the use of no greater pressure than the
hand can produce when passed over a sheet of paper, may be made by boiling
away nearly half of some ordinary writing fluid and then adding as much
glycerine.

A GOOD PASTER.

Let a little starch lie in vinegar over night. Pour in boiling water,
stirring briskly till it thickens. It will keep better if a few drops of
carbolic acid are added. A very little corrosive sublimate wi