Materials Required:—

Two gas mantle boxes, a piece of thin bladder or greaseproof paper, many yards of thin twine.

This can be made of two of the boxes used for incandescent gas mantles; the box for the larger inverted mantles is best. Remove the lids from each end and cut off the rims carefully, so that you have two neat rings of cardboard. Slip one of these on to one end of each box and over each rim tightly tie a circle of greaseproof paper—such as is used for covering jam pots or parcelling butter. Better still, use a piece of bladder from the butcher's. Fasten this down very tight and firm, and through the middle of each paper or bladder insert and knot the end of a fine piece of string which can be ten or more yards in length. If this is held taut without touching anything between the two boxes, you can whisper from end to end and the voice will be heard quite distinctly.