98 The Microscope. 



nitrate of silver when required, regardless of the black 

 stains which will presently appear upon it. The salts 

 will dissolve quickly in their compartments, and as 

 they will (except coloured ones, as the sulphate of 

 copper,) appear like clear water, you will find the con- 

 venience of having each labelled. 



The microscope should now be properly arranged, 

 because in many cases the process of crystallization is 

 very rapid, and the best effects would be lost during a 

 few minutes of delay. The tube should be inclined 

 slightly, and the power employed should be about sixty 

 diameters, which serves for most crystals. A slide 

 should be laid on the stage, with a scrap of paper or 

 some small object placed upon its surface. The focus 

 must be adjusted on this, and if the crystallization is 

 to be viewed as an opaque object, a good light must 

 be thrown upon it from the bull's-eye lens. All being 

 ready, the scrap of paper may be removed, and a drop 

 of the solution lifted by one of the glass rods or 

 narrow slips, and placed on the slide. For exhibiting 

 metallic crystals dark slides will be found very con- 

 venient.* 



The copper or zinc filings for dropping into the 

 solution must be in readiness. It is worth while to 

 make deep little envelopes to contain them, like those 

 in which small garden-seeds are sold. A little of the 

 filings can be shaken on to the flap of the envelope, 



* Mr. Dancer, of Manchester, has kindly presented some of these 

 dark slips of glass to me, and has furnished me with information on 

 the subject of crystallization, as well as of microscopic photo- 

 graphy. 



