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Profs. W. E. Ayrton and John Perry. [Dec. 12. 



box at an angle of 80° with the horizon, the half of the monld on 

 which the design has been cut being uppermost. Finally, the molten 

 speculum metal is run into a number of moulds at the same time, 

 which, when cold, are broken up and the castings removed. 



Mirrors cast in a mould, in which the design has been cut by hand, 

 are called ichi mai bulii, " mould used once," and are regarded as 

 " artists' proofs," as the design on the back is well denned. To form 

 subsequent moulds the two halves are pressed, when the clay is wet, 

 on an ichi mai buki mirror, and the pattern is this way transferred, 

 but the designs on the backs of the mirrors cast in such moulds are 

 not as clear as on an ichi mai buJci mirror, which therefore sells for a 

 much higher price. 



Curving the Surface. — The rough mirror is first scraped approxi- 

 mately smooth with a hand-scraping tool, and as this would remove 

 any small amount of convexity, had such been imparted to it in cast- 

 ing, it is useless to make the mould slightly convex. If, however, a 

 convex or concave mirror of small radius is required, then the surface 

 of the mould is made concave or convex. On the other hand, to pro- 

 duce the small amount of convexity which is possessed by ordinary 

 Japanese mirrors the following method is employed, if the mirror is 

 thin, and it is with thin mirrors we have especially to deal, since it is 

 only in these mirrors that the apparent reflection of the back is 

 observed.. The mirror is placed face uppermost flat on a wooden 

 board, and then scraped or rather scratched with a rounded iron rod 

 about half an inch in diameter and a foot long, called a megebo, " dis- 

 torting rod," so that a series of parallel scratches is produced, which 

 causes the face of the mirror to become convex in the direction at 

 right angles to the scratches, but to remain straight parallel to the 

 scratches, in fact it becomes very slightly cylindrical, the axis of the 

 cylinder being parallel to the scratches. This effect is very clearly 

 seen by applying a straight-edge in different ways to the face of an 

 unpolished mirror which has received a single set of scratches only. A 

 series of scratches is next made with the megebo in a direction of right 

 angles to the former, a third set intermediate between the two former, 

 and so on. the mirror each time becoming slightly cylindrical, the axis 

 of the cylinder in each case being parallel to the line of scratches, so 

 that eventually the mirror becomes generally convex. Some work- 

 men prefer to make the scratches with the megebo in the form of small 

 spirals, others in the form of large spirals, but the general principle of 

 the method employed with their mirrors appears to be always the 

 same, — the face of the mirror is scratched with a blunted piece of 

 iron, and becomes slightly convex, the back, therefore, becoming 

 concave. 



After the operation with the " distorting rod" the mirror is very 

 slightly scraped with a hand-scraping tool to remove the scratches 



