Method for Learning
Whenever possible, objects should be illuminated by sunlight or the light of a lamp with a thick wick: they appear better on paper. The opening of the convex glass should not be the same, for the reasons given in No. 27, to which we refer the Reader.
To make this device more portable, it must be given the shape of a large book, and the sides attached to each other with hinges and hooks so they can be folded upon one another, and folded in a way that side F, opposite to side E, can rest on base M, and then side E on side F. Then, fold the half-round L over the top D of the box, after removing the supports, the mirror and the pipe, they will be laid one on the other on side E. And since the top D must be attached with hinges to the back of the box BC, this back will fold on L and D, forming the book cover, which can be made to also hold the mirror, the supports that hold it, and the pipe that carries the convex glass. Two hooks will be placed at I and H, as well as on the opposite side, to keep the book closed.