e glass should be wetted with the wine.

_Cat-Boxes._

Every school-boy knows how to make these. They are not the boxes made by
cutting slits in paper. They are simply made by folding, and are then
blown out like the "frog," which is also made of folded paper.

_Liquid Beads._

Instead of melting gold, water rolled on to a table thickly dusted with
lycopodium, or other fine dust, or quicksilver rolled or thrown upon a
smooth table, will show the difference in the shape of large and small
beads perfectly. A magnifying-glass will make the difference more
evident. In using quicksilver, be careful that none of it falls on gold
or silver coins, or jewellery, or plate, or on the ornamental gilding on
book-covers. It will do serious damage.

_Plateau's Experiment._

To perform this with very great perfection requires much care and
trouble. It is easy to succeed up to a certain point. Pour into a clean
bottle about a table-spoonful of salad-oil, and pour upon it a mixture
of nine parts by volume spirits of wine (not methylated spirits), and
seven parts of water. Shake up and leave for a day if necessary, when it
will be found that the oil has settled together by itself. Fill a
tumbler with the same mixture of spirit and water, and then with a fine
glass pipe, dipping about half-way down, slowly introduce a very little
water. This will make the liquid below a little heavier. Dip into the
oil a pipe and take out a little by closing the upper end with the
finger, and carefully drop this into the tumbler. If it goes to the
bottom, a little more water is required in the lower half of the
tumbler. If by chance it will not sink at all, a little more spirit is
wanted in the upper half. At last the oil will just float in the middle
of the mixture. More can then be added, taking care to prevent it from
touching the sides. If the liquid below is ever so little heavier, and
the liquid above ever so little lighter than oil, the drop of oil
perhaps as large as a halfpenny will be almost perfectly round. It will
not appear round if seen through the glass, because the glass magnifies
it sideways, but not up and down, as may be seen by holding a coin in
the liquid just above it. To see the drop in its true shape the vessel
must either be a globe, or one side must be made of flat glass.

Spinning the oil so as to throw off a ring is not material, but if the
reader can contrive to fix a disc about the size of a threepenny-piece
upon