In place, however, of a box carried upon the telescope-tube, a darkened room (or true _camera obscura_) contains the receiving sheet.
A chamber is to be selected, having a window looking towards the south--a little easterly, if possible, so as to admit of morning observation.

All windows are to be completely darkened save one, through which the telescope is directed towards the sun.

An arrangement is to be adopted for preventing all light from entering by this window except such light as passes down the tube of the telescope.

This can readily be managed with a little ingenuity.

Mr.Howlett describes an excellent method.