away the first figure, 1, }
and adding it to the last figure, 2, } 13
the sum is }
Which added to Robert's age 22
----
Gives George's age, which is 35

_The Boundless Prospect._

Take a square box, about six inches long and twelve high, or of any
other proportionate dimensions. Cover the inside with four flat pieces
of looking-glass placed perpendicular to the bottom of the box. Place
at the bottom any objects you please, as a piece of fortification, a
castle, tents, soldiers, &c. On the top, place a frame of glass shaped
like the bottom of a pyramid, as in Fig. 8, and so formed as to fit on
the box like a cover. The four sides of this cover are to be composed
of ground glass, or covered inside with gauze, so that the light may
enter, and yet the inside be invisible, except at the top, which must
be covered with transparent glass: when you look through this glass,
the inside will present a pleasing prospect of a boundless extent;
and, if managed with care, will afford a deal of amusement.

[Illustration: Fig. 8.]

_To set Fire to a combustible Body by Reflection._

Place two concave mirrors at about twelve feet distance from each
other, and let the axis of each be in the same line. In the focus of
one of them place a live coal, and in the focus of the other some
gunpowder. With a pair of strong bellows keep blowing the coal, and
notwithstanding the distance between them, the powder will presently
take fire.

The mirror may be either made of glass, metal, or pasteboard gilt.

_To find the Number of Changes that may be rung on Twelve Bells._

Multiply the numbers from 1 to 12 continually into each other, as
follow: and the last product will give the number required.

1
2
--
2
3
--
6
4
--
24
5
----
120
6
----
720
7
-----
5,040
8
------
40,320
9
-------
362,880
10
---------
3,628,800
11
----------
39,916,800
12
-----------
479,001,600

_To find how many square Yards it would require to write all the
Changes of the Twenty-four Letters of the Alphabet, writte