the front wall—that opposite the entrance—of the first room, are the units; on the right-hand wall the tens; on the left hand the twenties; on the fourth wall the thirties; and on the floor the forties. Numbers 10, 20, 30 and 40, each find a place on the roof above their respective walls, while 50 occupies the centre of the room. One room will thus furnish 50 places, and ten rooms as many as 500. Having fixed these clearly in the mind, so as to be able readily and at once to tell exactly the position of each place or number, it is then necessary to associate with each of them some familiar object (or symbol) so that the object being suggested its place may be instantly remembered, or when the place be before the mind its object may immediately spring up. When this has been done thoroughly, the objects can be run over in any order from beginning to end, or from end to beginning, or the place of any particular one can at once be given. All that is further necessary is to associate the ideas we wish to remember with the objects in the various places, by which means they are easily remembered, and can
