The next thing to which we can turn our attention is a grid for the sink. To make it, take two pieces of wood 10 in. long by 3 in. wide and 1 in. thick, and a few laths, like those used for window blinds, 144 in. long ; nail these together about an inch apart, as shown in fig. 22, when the grid will be complete.
We must now make some provision for a supply of water for We may, of course, make shift with a jug and a pail, but a far better plan will be to procure from the nearest grocer one of the tins in which glycerine is stored. These are about twice the size of an ordinary biscuit box, but watertight, and made of much stouter tin ; they hold about two gallons of water. This should be placed on the right-hand side cf the top shelf, and a piece of ordinary " compo " gas-pipe should be soldered to the bottom, con ducted down the upright and carried to the point " X" just above the sink, where a small tap should be soldered. While this supply will, of course, be of no use for plate-washing and other purposes where large quantities of water are required, yet it will be quite sufficient for the ordinary purposes of development, for supplying water for mixing the developer, for rinsing the plates after development, and for the cleansing of measures, dishes, etc. In order to carry off the waste from the sink a piece of flexible india-rubber tube should be attached to the short length of pipe which, it will be remembered, we had soldered to the bottom of our zinc tray, and thence conducted into a pail or other suitable receptacle. If the capacity of the vessel be equal to that of the water-tank, and we make it a rule never to fill the one without emptying the other, an overflow will be rendered impossible. Two coats of Aspinall's enamel over the whole will complete our labours ; that is to say, if we only wish to work at night, or can completely exclude daylight from the room by means of heavy curtains or a screen constructed according to the method described in the last chapter. If, however, it should not be possible so to arrange matters the apparatus can, with very little further trouble, be so modi fied as to form in itself a portable dark-room.
To make the necessary alterations, screw firmly two additional uprights, at DD, in fig. 20 ; and then fill in the sides with thin boarding in the same manner as the back was filled in, in C C C (fig. 20). When the sides have been so filled in the roof may be covered in the same way. The next thing to do will be to make all the woodwork thoroughly lightproof, and the best way of doing so is to paste the outside over with one thickness of stout carpet paper, covering that, in turn, with one thickness of stout Willesden waterproof paper ; the inside should also be lined with the latter, as it may then be washed with impunity when it becomes dirty or stained with chemicals. We have
now to arrange about keeping out the light from the back, and to effect this a curtain must be provided. It should be made of one thickness of black, and one of orange twill ; and sufficient material must be purchased to make, when sewn together, a curtain at least one and a half times as wide as the front of the bench, and its length should be such that it just touches the floor. It must be nailed with tin-tacks to the top and sides of the cabinet. The extreme ends should first be tacked to the top of the uprights, and then the " slack," as it were, got rid of by folding in pleats and tacking each pleat. The tacking should be continued down the sides to just below the table. In order to facilitate the operator's movements in getting in and out, the curtain should be cut up the middle of the back for about three feet of its length from the ground. When the person using the cabinet wishes to change or develop a plate, he lifts the curtain, seats himself on a chair, gathers the loose ends of the curtain round him so as to exclude all light ; and in order to assist him in doing so, a few buttons and loops of elastic should be sewn on the curtain inside, which will prevent it from suddenly slipping and admitting an unex pected ray of light. The exact position for these cannot be indicated, but there will be no difficulty in finding the most suitable places.
Some provision for ventilation should now be made, for without it the air in the interior of the cabinet would soon be as foul as the notorious "Black Hole" of Calcutta. Cut, with the keyhole saw, a hole, 3 in. in diameter, in the roof, to which affix an elbow-joint length of stove pipe. This will carry off the heated and vitiated air from the top of the tent. But it will also be necessary to provide a means for pure air to enter and take the place of that which goes out. A sufficient quantity might filter through the curtain, but it will be well not to depend upon that source of supply. At the back of the table or bench, therefore, another hole, 3 in. in diameter, should be cut; and a second elbow-joint affixed in the same manner as before. Care should be taken to turn the mouth of this so that it points in a direction opposite to that in which the window of the room is situated.
If the foregoing directions have been carefully carried out, the reader should be in possession of a developing cabinet, which, although it will have cost him but a few shillings to construct, will, for all practical purposes, be as convenient and useful as a commercially-made article costing as many pounds.