| Lead | 10 | parts. |
| Natural sulphide of lead and antimony | 10 | „ |
| Copper | 80 | „ |
| 100 | ||
“After being cooled, the melting box and molds are crushed and the mirrors taken away. These are then cut, scoured, and filed until they are roughly finished. They are then first polished with a polishing powder called to-no-ki, which consists of the levigated powder of a soft kind of whetstone (to-ishi) found in Yamato and many other places. Secondly, they are polished with a piece of charcoal and water, the charcoal of the wood ho-no-ki (Magnolia hypoleuca) being preferred as the best for the purpose. When the surfaces of the mirrors are well polished they are covered with a layer of mercury amalgam consisting of quicksilver, tin, and a little lead. The amalgam is rubbed vigorously with a piece of soft leather, which manipulation must be continued for a long time, until the excess of mercury is expelled and the mirrors have a fine, bright reflecting surface.”
MAGIC MIRRORS.
The following article on magic mirrors by MM. Bertin and Dubosq outlines several interesting experiments.
“The people of the Far East, the Chinese and the Japanese, in bygone times were acquainted with metallic mirrors only; and even to-day they make only these. They are made of speculum metal, of various forms and sizes, but always portable. One of the faces is polished and always slightly convex, so that its reflection gives images which are reduced in size; the other face is plane or slightly concave, and always has cast on it ornaments which are in relief. Among the many mirrors thus constructed there are a few which possess a wonderful property: when a beam of the sun’s light falls upon the polished surface and is reflected on a white screen, we see in the disk of light thus formed the image of the ornamentation which is on the back of the mirror. The Chinese have long known of these mirrors and value them highly; they call them by a name which signifies ‘mirrors which are permeable to the light.’ We, of the West, call them ‘magic mirrors.’
“Very few persons had seen magic mirrors till Mr. Ayrton, professor of the Polytechnic School at Yeddo, exhibited several which he had brought with him from Japan, and he experimented with them as already mentioned.
“In the meantime I received a visit from M. Dybowski, my former pupil, who had returned from Japan, where for two years he had been the colleague of Professor Ayrton. He brought back with him as objects of curiosity four temple mirrors, that is to say, antique mirrors; these are far superior to those of modern production, for their manufacture has been nearly abandoned by reason of the introduction of the silvered mirrors of Europe. We tried them together; three were circular, and the thinnest of them, which is a disk of 15.3 centimeters in diameter, was found to be slightly magic.
“To try such a mirror we reflect a sunbeam from its polished surface to a white cardboard about one meter distant. But to obtain the very best effects we must illuminate the mirror with a diverging pencil of light; this pencil is made still further divergent by reflection from the mirror, because its reflecting surface is convex. We can now receive the reflected rays on a screen at a greater distance, and we at once see distinctly the magnified image of the ornamentation on the back of the mirror. These raised designs appear on the screen in white on a dark ground. The image thus made by our mirror was confused, because it was not a good one; had it been properly made, the image would have been sharply defined. I then knew of no means by which I could make it give better effects.
“The means by which the mirror could have been improved were first pointed out by M. Govi in the second of his two papers. It is a consequence of the true theory of magic mirrors. The theory was not reached at once. I proposed to M. Dubosq to associate himself with me in order, first, to repeat the experiments of the learned Italian, Govi, and then to study generally the interesting phenomena of magic mirrors, in the hope of being able eventually to reproduce them in his workshops. At first we had only at our disposal the mirror brought from Japan by M. Dybowski, and which gave confused images with the reflected solar rays. These images became very sharply defined when we had heated the back of the mirror with a gas lamp, and it gave very magic effects.