Mr Witham's Observations on Fossil Vegetables. 189 



microscope. To facilitate this part of the grinding, the lapi- 

 dary will find it advantageous to fix the glass in a groove made 

 in a small piece of wood, of which half inch thick deal will 

 answer the purpose. The groove in the wood should be a 

 little less deep than the thickness of the glass, and the wood 

 itself need not project more than half an inch beyond each side 

 of the glass. 



" A lapidary, by attending to the above directions, will find 

 no difficulty in reducing any piece of petrified wood to that 

 degree of thinness sufficient to render its structure visible ; and 

 any one, even without the aid of the mechanism employed by 

 the lapidary, may accomplish that object by attending to the 

 following directions. 



" The position of the fibres of the wood having been ascer- 

 tained, let a thin piece be chipped off by a blow of a hammer, 

 in a direction perpendicular to the length of the fibres. Let 

 the chip thus obtained be cemented to any small bit of wood 

 by common lapidaries 1 cement (a compound of 1 part bees' 

 wax, 1 part pitch, 4 parts rosin, 16 parts of a mixture of brick- 

 dust and whitening,) to enable the operator to hold it firmly 

 while the grinding is going on. That side of the chip which 

 approaches nearest to a perpendicular to the length of the fibres, 

 must be ground flat, by giving it a rapid circular motion with 

 the hand, on a piece of sheet-lead lying horizontally on a table, 

 and supplied with a little emery, size No. 1, moistened with 

 water. When the emery ceases to act, the muddy matter re- 

 maining may be removed, and a fresh portion of emery appli- 

 ed ; and this must be repeated until the surface of the chip 

 has become perfectly flat. The sheet of lead must then be re- 

 moved, and a piece of flat sheet copper substituted, and the 

 surface of the chip ground as smooth as may be, by flower of 

 emery, freed from its coarser parts. The surface may then be 

 polished by friction with crocus or rot-stone, on a transverse 

 section of any soft wood. 



" When the polishing is finished, the chip must be detached 

 from the wood to which it was cemented, and the polished sur- 

 face cemented by Canada balsam to a piece of plate-glass, in 

 the manner above described, and then ground thin, and polish- 

 ed as before." 



