4 ON THE CONSTRUCTION AND USE OF 



inside with a mixture of beeswax and rosin (equal parts). At opposite ends of one 

 diameter two narrow pieces of wood, a a' , \ of an inch thick, are cemented. They 

 are to keep the face of the mirror from the bottom of the vessel, and permit of a 

 rocking motion being given to the glass. Before nsing such a vessel, it is necessary 

 to touch any cracks that may have formed in the wax with a hot poker. A spirit 

 lamp causes bubbles and holes through to the tin. The vessel too must always, 

 especially if partly silvered, be cleaned with nitric acid and water, and left filled 

 with cold water till needed. Instead of the above. India-rubber baths have been 

 occasionally used. 



3d. In order to secure fine and hard deposits m the shortest time and with weak 

 solutions, it is desirable, though not necessary, to warm the glass slightly. This is 

 best done by putting it in a tub or other suitably sized vessel, and pouring in water 

 enough to cover the glass. Then hot water is gradually stirred in, tiU the mixture 

 reaches 100° F. It is also advantageous to place the vessels containing the in- 

 gredients for the silvering solution in the same bath for a short time. 



4th. On taking the glass out of the warm water, carry it to the silvering vessel — 

 into which an assistant has just previously poured the mixed silvering solution — 

 and immediately immerse it face doAvnwards, dipping in first one edge and then 

 quickly letting down the other tiU the face is horizontal. The back of course is 

 not covered with the fluid. The same precautions are necessary to avoid streaks 

 in silvering as in the case of putting a collodion plate in the bath. Place the 

 whole apparatus before a window. Keep up a slow rocking motion of the glass, 

 and watch for the appearance of the bright silver film. The solution quickly turns 

 brown, and the silver soon after appears, usually in from three to five minutes. 

 Leave the mirror in the liquid about six times as long. At the expiration of the 

 twenty minutes or half hour lift it out, and look ' through it at some very bright 

 object. If the object is scarcely visible, the silver surface must then be washed 

 with plenty of Avater, and set on edge on bibulous paper to dry. If, on the con- 

 trary, it is too thin, put it quickly back, and leave it until thick enough. When 

 polished the silver ought, if held between the eye and the sun, to show his disk 

 of a light blue tint. On coming out of the bath the metaUic surface should have 

 a rosy golden color by reflected light. 



5th. When the mirror is thoroughly dry, and no drops of water remain about 

 the edges, lay it upon its back on a thorouglily dusted table. Take a piece of the 

 softest thin buckskin, and stuff it loosely with cotton to make a rubber. Avoid 

 using the edge pieces of a skin, as they are always hard and contain nodules of 

 lime. 



Go gently over the whole silver surface with this rubber in circular strokes, 

 in order to commence the removal of the rosy golden film, and to condense the 

 silver. Then having put some very fine rouge on a piece of buckskin laid flat on 

 the table, impregnate the rubber with it. The best stroke for polishing is a motion 

 in small circles, at times going gradually round on the mirror, at times across on 

 the various chords (Fig. 2). At the end of an hour of continuous gentle rubbing, 

 with occasional touches on the flat rouged skin, the surface will be polished so as 

 to be perfectly black in oblique positions, and, with even moderate care, scratchless. 



