BULLETIN 39, UNITED STATES NATIONAL MUSEUM. 



[10] 



to have a sufficient quantity of balsam already evaporated and in the 

 form of sticks or lumps. 



When the balsam on the glass is of the proper condition and very 

 fluid as well as free from bubbles, the hot chip is placed upon it, one 

 edge first and the other gradually lowered in such a way as to prevent 

 the inclusion of air bubbles. A needle point set in a wood handle (fig. 

 11) and a small pair of spring forceps (fig. 12) will be found serviceable 

 for this purpose. The chip is then pressed into the balsam and as 

 closely to the glass as possible. It is best to work the chip back and 

 forth a little in order to accomplish this. If too much balsam is allowed 

 to remain between the glass and stone chip the section will be found to 

 remain thick in the center and grind away on the edges, and ultimately 

 become lost or so reduced in size as to be of little value, before the desired 



FiG, 13. — Mounting frame. 



thinness is reached. This matter of mounting is best carried on by 

 means of an iron plate sufficiently thick to retain a level surface, which 

 is supported at the four corners and heated by means of a lamp beneath 

 (fig 13). After the chip is once in place, the slip is removed from the 

 plate and placed in a horizontal position uiDon the table to cool. 



The grinding now is carried on precisely as before, the glass serving 

 as a holder for the fingers, and, being transparent, allows the worker to 

 observe just the condition of the slide at any moment. Care needs be 

 exercised as the section becomes thinner, and it is well to have two or 

 more plates upon which emery of different degrees of fineness is used. 

 This, however, is not essential, though after the section is well on toward 

 completeness a single coarse grain coming in contact with it may create 

 sad havoc. The final grinding, the writer has found, can be best done 

 on a sloping j)late of ground glass (fig.l4), using only the finest washed 



