22 PEEl'AEATIOX AX1) MOUNTING 



an account here ; but the author believes that most, if not 

 all, of the same effects may be produced by the employment 

 either of a thick plate of metal placed upon the stage, or of 

 a thin water-hath, which may he heated by a spirit or gas 

 flame, after the glass slide shall have been placed on it. 

 They should both be properly fitted with thermometers. 



Of the decomposition of salts by electricity, and their re- 

 duction to the metallic state, it is not necessary to speak 

 here, but such effects are very beautiful, and the resulting 

 crystallization may easily be watched. 



Dr. Beale speaks very favourably of the inverted micro- 

 scope devised by Dr. Lawrence Smith, U.S.A., by which 

 objects may be viewed from their under instead of from their 

 upper surface, and at the same time heated (or re-agents 

 applied to them) without any risk of dimming or injuring 

 the objeot-glass by vapours thus raised. The optical part 

 is so fitted to the base that it may be drawn away from be- 

 neath the stage (to make room for the application of the 

 lamp, or) for the sake of changing the powers. 



HTH DIVISION. 



It is evident that in all these plans an amount of evapo- 

 ration is constantly going on, which will eventually dry and 

 so spoil the object, unless obviated. Frey, therefore, describes 

 a "moist chamber" invented by Recklinghausen for this 

 purpose. It consists of a glass ring, more or less high, 

 which has been cemented by its edge to a broad glass slide. 

 A tube of thin rubber is then firmly fastened about the ring. 

 The upper end of this tube is also fastened around the tube 

 of the microscope. In order to keep the place thus enclosed 

 saturated with moisture, some small pads of wetted bibulous 

 paper, or pieces of elder pith also saturated with fluid, are to 

 be enclosed with the object, which in this case need not be 

 covered with thin glass in the usual manner. It is con- 

 ceivable also that this apparatus may easily be converted 

 into a gas chamber, by fixing two small, light vulcanized 



