the amalgam of tin and mercury is rubbed in with a stiff straw brush, and polished off with soft paper. Thicker mirrors are sometimes pared down with a knife to the convex shape: they seldom or never show magic properties. The knife is also used to pare down any portion which in the operation _mege_ may have become too convex. The convexity is tested from time to time by applying a concave wooden form. Professor Ayrton was of opinion that the magic properties were conferred during the operation of scraping with the _megebo_, the thicker parts of the mirror yielding less, and therefore being polished down more than the thinner parts. He also noted that if the face was scored by the _megebo_ with parallel lines in one direction only, the convexity acquired was cylindrical. His conclusion was: “It appears then that the magic of the Eastern mirror results from no subtle trick on the part of the maker, from no inlaying of other metal, or hardening of portions by stamping, but merely arises from the natural property possessed by thin bronze of buckling under a bending stress, so as to remain strained in the opposite direction after the stress is removed. And this stress is applied partly by the ‘distorting rod,’ and partly by the subsequent polishing, which, in an exactly similar way, tends to make the thinner parts more convex than the thicker.” The researches of Ayrton and Perry may be said to have determined once and for all the main cause of the magic properties. No one has since disputed the principal propositions of their memoir, though it is certain that the differences of curvature may be produced in several varieties of operation.