78 H.J. Grayson : 



the specimens are successively claiuped in the laro-e specimen 

 holder of the slicinc- machine, and a piece, large enough for a 

 section, is sliced away : the whole 'JO being thus treated. 

 Meantime, the balsamed slips will have l)ecome suthcienth- 

 hardened. Each slip should be separately tested, when cool, 

 with forceps or knife ; the hardened balsam should indent with 

 moderate pressure without splintering. 



The sliced face of each specimen is now, for a few seconds, 

 held upon the finest revolving lap, which is fed with F.F. cai-- 

 borundum, and moistened with water containing about 1 5th 

 of its volume of Glycerine, which maintains a rapidly revolving 

 disc sufRciently moist, without excess, for a long time. Each 

 specimen requires only a brief treatment, and if the lap is in 

 first class order no furtlier preparation should be required. 

 Usually, however, it is safer to give each specimen a few sweeps 

 by hand, upon a slate or glass lap. the surface of which should 

 be accurately true or flat. After washing and drying, the 

 specimens are ready for attachment to the balsamed slips. 

 This is done by heating them sufficiently to occasion discom- 

 fort when held against the hand for a few seconds ; the slip 

 being correspondingly heated, the specimen is pressed home on 

 the slip, taking care to exclude all air Imbbles. As each slide 

 is dealt with it is placed on a second jtlate of glass {'■^h x 1}, in. 

 X 5/16th in,, thick, the blocks being strictly uniform), and 

 heated to melt the beeswax, which is used to hold the slip in 

 position during its subsequent treatment. After the entire 

 series has thus been treated and allowed to cool, each glass 

 plate or block in turn is clamped in the special holder, and the slicer 

 passed through the rock close to the glass of the mounting 

 slip. With everA'thing in good order, this may l)e done to 

 Avithin .5 mm. ; the thickness being regulated by means of two 

 strips of thin sheet iron, held in position on the slip Avhile the 

 cut is being started. 



The series having been sliced, each section is ground to witliin 

 .1 mm., on the coarse grinding lap, using F carborundum, or 

 certainly not a coarser grade than 220. After washing, the 

 grinding is completed on the finest revolving lap, and if the 

 latter is time and the operator experienced, scai-cely any fur- 

 ther grinding will l)e re(]uired. With a sufficiently finely graded 



