uthorities) amounts to
_four hundred thousand billion_ cubic feet, which, if piled up, would
form a mass one hundred and forty miles long, as many broad, and as many
high, or, otherwise disposed, would cover the whole of Europe, islands,
seas, and all, to the height of the summit of Mont Blanc, which is about
sixteen thousand feet in height.

If salt, however, were only to be obtained from the sea, the people who
live on immense continents would have great difficulty in supplying
themselves with it; and here you see how kindly Providence watches over
the comfort of human creatures, for nature has provided that the sea, on
leaving those continents, all of which were once overspread with it,
should deposit vast quantities of salt, sufficient to provide for the
necessities of the inhabitants of those parts. In some places the salt
is exposed on the surface of the ground in a glittering crust several
inches thick; in others, thicker layers have been covered over with
other substances, so that salt now requires to be dug for like coal or
any other mineral. Salt is found in this last shape in almost every part
of the world; though in the vast empire of China it is so scarce that it
is smuggled into that country in large quantities.

[Illustration]

A SUN-DIAL.

Our young friends would, we doubt not, like to know how to make a
sun-dial that will give the time very accurately. Common sun-dials
depend on the shadow of a post, which is thick and heavy, and affords
only a very rough idea of the time. But the one we are going to tell
them about will show the time as precisely as a clock. And it is quite
easy to make. It has, in the first place, a face set up slanting on a
pedestal. The proper slant answers to the latitude of the place. At and
near New York it should be about forty-one degrees from the
perpendicular, or a little more than half upright. The face is divided
into hour spaces, just like the face of a clock, but the whole circle is
not used. A semicircle is all that the sun can traverse, except in the
long days of summer. The fourth part of a circle is about all that can
be used in ordinary windows. It will answer for the hours between nine
o'clock and three. It is divided into six equal parts for the hour
spaces, and each of these is subdivided for the minutes. If the radius
of the circle be one foot, the minute spaces will be about one-sixteenth
of an inch, or about the same as on the face of a watch. The d