Micro-Metallography. By J. E. Stead. 279 



be kept moist by allowing water to fall upon its surface from the 

 reservoir D. In the bottom of this reservoir there is placed a plug 

 of cotton-wool to prevent the passage of any grit. 



When polishing copper, brass, and softer metals the No. 4 block 

 is lubricated with oil instead of water. 



It will be noticed that in the description just given there is 

 nothing required excepting what can be obtained commercially. 



The emery paper can be obtained i'rom any ironmonger, the cloth 

 from any tailor, and the diamantine powder from any jeweller. 



Mounting the Specimens foii Microscopic Examination. 



There have been several devices described for the purpose of 

 mounting specimens upon glass slides for microscopical examination. 

 Mr. Merrett uses a mixture of wax, but for my own part I find that 

 there is nothing better than the plasticine used by children for 

 model making, a material which constantly remains plastic both in 

 summer and winter, and has, moreover, the good property of 

 adhesiveness. This can be obtained from any kindergarten stores, 

 at very little cost, or from dealers in polishing apparatus. 



A most accurate and certain method of obtaining the polished 

 surface of the metal in true parallel plane with the plane of the 

 Microscope slide is to place the polished surface of the specimen 

 upon a piece of plate-glass, and to place over tins a short cylinder 

 of brass or other metal, the two ends of which are parallel, and 

 whose height is sufficient to extend a little beyond the back of the 

 specimen. A piece of plasticine having been stuck on to the glass 

 slide, this is pressed upon the specimen until the glass rests on the 

 upper end of the cylinder. The slide is then removed, together 

 with the specimen adhering to it. 



Messrs. Watson and Sons have one or two devices for levelling 

 metal sections on the stage of the Microscope, one of which has 

 been designed by Mr. Eosenhain ; and Messrs. Swift and Sons have 

 prepared, to my design, a device which is most satisfactory. 



Messrs. Heycock and Neville have a very neat way of marking 

 their glass slides. Instead of plain slips they use ground glass, 

 and write in pencil upon the frosted surface a description of the 

 nature and character of the object. The necessity of having some 

 simple method of marking will be obvious when it is known that 

 it is often necessary to immerse the metal sections after mounting in 

 etching fluids. Gummed labels would come off and be lost under 

 such treatment. In practice it has been found more convenient to 

 use glass slips 2 in. by 1 in. instead of those 3 in. by 1 in. 



