method of revivifying hydrated calcium sulphate has recently formed
the subject of a patent (Eng. pat., No. 15,406).

The method described in the specification consists in reducing the
materials (waste moulds, etc.) to small lumps, and baking between the
temperatures of 95° and 300°. It is mentioned that the whole of the
water must not be expelled. This is no doubt correct, but it must be
effected by regulating the _time_ of baking, since by prolonging the
operation all the water of crystallization can be expelled far below
300°. To secure even baking the mass is kept stirred by mechanical
stirrers, a necessary precaution, since the operation is to be carried
out in an ordinary kiln. The process is stopped when a portion of the
plaster is found to set in the required time, a method of regulation
which will probably be found to work well in practice.--_Chem. Trade
Jour._

* * * * *




SPACING THE FRETS ON A BANJO NECK.

BY PROF. C.W. MACCORD.


The amateur performer on the banjo, if he be of a mechanical turn, is
often tempted to exercise his skill by making an instrument for
himself; and the temptation is the greater because he can confine
himself to the essentials. The excellence of a banjo in respect to