��Popular Science Monthly
��and developer from soaking through to the drawer below. The use of a water- bath for keeping the developer cool will be found a great convenience. It will be noticed that the running water in the wash-tank is in contact with the hypo- tank, thus insuring cold hypo. In case it is intended to work with only small plates or films the hypo and wash tank shown in Fig. i to 4 may be supplanted by the one shown in Fig. 5. This consists of a galvanized-iron tank i ft. square and i ft. high, which serves as a wash-tank. In this, at one end, is placed a glass or hard rubber battery jar such as may be obtained from any of the larger electrical dealers. This jar serves as a hypo-tank.
The rheostat. Fig. 2, is a 300-ohm rheostat of half-ampere capacity and has all the range needed for dimming a 50- watt red lamp. If a "dimalight" is obtainable it will be found to be a satisfactory substitute for the rheostat. Care should be taken to paste a piece of black paper over the tip of the red lamp as the tips of such lamps are often uncolored, allowing white light to pene- trate into the room.
In Fig. 2 the white light is shown as a lOO-watt Mazda C-2 lamp behind a ground glass. It therefore serves both as a white light and as a diffuse light for printing.
Attention is called to the use of cur- tains in the doorway as a means- of economizing space in case the dark- room is built out like a closet in a large room. Two curtains are hung on sep- arate rods as shown in Fig. 6. The out- side edges are fastened permanently to the doorway. The inside edges are fastened to sticks about i in. square. These sticks act as weights and prevent the curtains from blowing in and out, causing light-leaks. Each curtain is wide enough to stretch completely across the doorway. A suitable housing as shown, painted black on the inside, prevents light from leaking over the top of the curtains. The curtains are made of double thicknesses of galatea. Such a closet darkroom requires artificial ventilation or it soon becomes unbear- able. An adequate scheme for ventila- tion is suggested in Fig. 2 and 7.
The second darkroom is more elabo- rate and is more adapted to professional use. The tanks and their arrangement
��are shown in Fig. 8, 9 and 10. The cost of construction may be reduced by sub- stituting the hypo and wash tank shown in Fig. 5. Attention is called to the method of drying the plates with the fan. The hypo and wash tank is shown in detail so as to be a guide to any who may care to construct a similar one. In Fig. II the switches governing the various lamps are not shown. The treadles will, however, indicate where these switches should be placed. In Fig. 12 is shown the general arrangement of tanks in a closet darkroom.
��A Comfortable Collar for the Horse
PADS used in the construction of any article add proportionately to its weight and in the making of horse collars the added burden is considerable; yet it is quite necessary to have sufficient
���Air cell substitute is more comfortable than the stuffed pads in a horse collar
padding against the horse's shoulder as a protection. The latest type of a collar made abroad is a pneumatic pad, built up similar to an automobile tire. Each side of the collar is a chamber of suitable shape to receive an inner air tube, which is blown up with a tire pump. Not only is the collar lighter than the ordinary one but it will fit better on the neck of the horse.