th. A sheet is folded
over and over again to see whether holes will appear at the corners
of the folds. It is examined under the microscope to see of what
kind of fibers it is made and how much loading has been used in its
manufacture. To test blotting paper, strips are also put into water
to see how high the water will rise on them.

Besides writing and wrapping papers and the various kinds of board,
there are many sorts which are used for special purposes. India paper,
for instance, is light, smooth, and strong, so opaque that printing
will not show through it, and so lasting that if it is crumpled, it
can be ironed out and be as good as new. This is used for books that
are expected to have hard wear but must be of light weight. There are
tissue papers, crepe papers for napkins, and tarred paper to make
roofs and even boats water-tight. If tar is brushed on, it may make
bubbles which will break afterwards and let water in; but if tar is
made a part of the paper itself, it lasts. Paper can easily be waxed
or paraffined, and will then keep out air and moisture for some time.
Better still, it can be treated with oil and will then make a raincoat
that will stand a year's wear, or even, if put on a bamboo frame, make
a very good house, as the Japanese found out long ago. Paper coated
with powdered gum and tin is used for packing tea and coffee. Transfer
or carbon papers so much used in making several copies of an article
on the typewriter are made by coating paper with starch, flour, gum,
and coloring matter. Paper can be used for shoes and hats, ties,
collars, and even for "rubbers." It has been successfully used for
sails for light vessels, and is excellent made into light garments
for hospital use because it is so cheap that it can be burned after
wearing. Wood pulp can be run through fine tubes into water and made
so pliable that it can be twisted into cord or spun and woven into
"silk." Not only water but also fire can be kept out by paper if it is
treated with the proper substances. An object can be covered with a
paste of wood pulp, silica, and hemp; and when this is dry, a coat of
water-glass will afford considerable protection. There has been some
degree of success in making transparent paper films for moving
pictures; and if these are coated with water-glass, they will not
burn. Paper can be so treated that it will either conduct electricity
or become a nonconductor, as may be desired. In Germany, a "sandwich
pa