the transposition-frame, or
arithmeticon, as it has been called. To these may added little
books, &c. The particular use of these articles will be shewn in the
succeeding pages.

The following is a representation of a lesson-post.

The _lessons_, pasted on wood, to render them sufficiently stiff, are
put into the grooves of the lesson-post; and can then be placed in any
position which is most convenient, and adjusted to any height, as the
master may see proper.

[Illustration: _a b_, is a slip of wood with a groove in it, fixed to
the post by means of the screws _c_ and _d_, on which slip are two
blocks _e_ and _f_; the bottom one, _f_, is fixed with a groove in
the upper side, for the lower edge of the board _g h_ to rest in; the
upper block, _e_, has a groove in the lower side, for the upper edge
of the board _g h_ to rest in, and rises and falls according to the
width of the board on the slip _a b_.--Instead of being made with
feet, the lesson post is generally, and perhaps better, fixed into
the floor of the school-room, and should be very slight, and 4 feet 4
inches in height.]

The following lesson-post has been found to answer better than the
preceding one; and is fixed in a socket, which prevents the necessity
of the cross-bar feet at bottom, and possesses this advantage, that it
may be taken out when done with, and hung up by the side of the
wall, so as to allow the area of the room to be quite clear of any
incumbrance, and to be used for any other purpose. No. 2, is the
socket which should be let into the floor and screwed fast to the side
of a joist, so as to keep it perfectly steady; the socket is to be
open at bottom so as to let the dust pass through: and No. 1, is a
plate, to fit over the socket, to come flush with the floor, to be put
over it when the lesson-post is taken out, to prevent too much dust
from getting into the socket. The little nich represented in plate
one, is too small for the pupils to get their fingers into, so as to
pull up the plate, but wide enough to allow the teacher to put a
very narrow key in, when he desires to pull up the plate to put the
lesson-post in the socket. No. 3, is a front view of the lesson-post,
containing the slides nipping the lessons between them; the other
figure represents a side view of the lesson post, and the small figure
at the left hand side represents the groove of the two sliders to
receive the lesson, and the back part of it the dovetails to clip,