OF MICROSCOPIC OBJECTS. 145 
The edge of this saw I charge with diamond-powder. To 
the edge of the saw I hold my specimen, and as it cuts I 
lubricate the edge with a small brush dipped in turpentine. 
With this method I have cut sections of fossil wood so thin 
that all its structure has been well defined and required 
nothing but mounting in balsam; this has been silicated 
fossil wood. In cutting calcareous fossil wood, I have to 
cut the sections thicker and grind them down. My grinding 
apparatus is composed of leaden laps, which I make to 
revolve in a horizontal position on the same upright spindle 
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