94 r Modern Microscopy. 



put the section into it ; apply a cover-glass, and press it 

 down until it adheres to the cement all round. Sections of 

 teeth are made in the same way. 



Rock Sections. Small pieces or slices of rocks are to 

 be ground on a zinc plate with the aid of emery-powder and 

 water until one side is quite flat and smooth. Then fasten 

 the polished surface to a square of glass with some dried 

 Canada balsam, as directed for bone, and allow it to cool. 

 Grind the other side on the zinc plate with coarse emery 

 and plenty of water. When moderately thin, take a piece 

 of plate-glass and some fine flour- emery, and rub the section 

 down as thin as possible. When thin enough, wash well in 

 water and dry ; then warm over a spirit-lamp, and with a 

 needle push the section off the glass into a saucer of benzole 

 or turpentine, and allow it to soak until all the balsam is 

 dissolved. Wash again in some clean turpentine, and 

 mount in Canada balsam in the usual way. Sections of 

 echinus spines, shells, and stones of fruits are prepared in 

 the same way as bones and teeth ; but when the grinding is 

 finished, the sections are to be passed through alcohol into 

 clove oil, then mount in Canada balsam in the usual way. 



LESSON 10. 



PREPARING AND MOUNTING ENTOMOLOGI- 

 CAL SPECIMENS FOR THE MICROSCOPE. 



Insects should be killed with chloroform. They are then 

 to be placed in methylated spirit, in which they may remain 

 until required for mounting. 



To Prepare an Insect for Mounting with Pressure 

 in Canada Balsam. (1) Transfer from methylated spirit 

 to' water, and let it soak for three or four hours to remove 

 spirit. 



(2) Place in liq. potassse, 10 per cent, of caustic potash 

 in distilled water, until soft. Some specimens will only 

 require a few hours in the potash, others want days, and 

 some even weeks, to soften. In all cases they must be 



