>4J 



e last pans of the protest are the most delicate d 

 all. We di-Mrr i.. make the section as thin as possible, 

 and for thai purpose < rubbing until after one 



Anal attempt we perhaps find to our dismay that great 

 pan of the slice has disappeared. I >t caution 



must consequently be used. The slide should be kept 

 as flat as possible, and looked at frequently, that th 

 indications of disruption may be detected nneat 



desirable or attainable depends in great measure upon 

 the nature of the rock. Transparent minerals need not 

 be so much reduced as more opaque ones. Some 



als, indeed, remain absolutely opaque to the last, 

 like pyrite, magnetite, and ilnu-r 



now ready for the microscope. It ought 



always to be examined with that instrument at this stage. 



HIS see whether it is thin enough, and if any 



ical tests are required they can readily be applied to 

 the exposed surface of the slice. If the rock has proved to 

 be very brittle, and we have only succeeded in procuring 

 a thin slue after much labour and several failures, nothing 

 further should be done with the preparation unless to 

 it with glass, as will he immediately explained, 



. not only protects it, I mt adds to its transparency. 

 Hut where the slice is not so fragile, and will bear 

 removal from its on . ed piece of glass, it 



should be transferred to one of the glass-slides < No. to). 

 irpose the preparation is once more placed on the 

 warm iron plate, and close alongside of it is put the glass- 

 slide, which has been carefully cleaned, and on the middle 

 of which a little Canada balsam has been dropped. The 

 heat gradually loosens the cohesion of the slice, wt 



