438 
ELEMENTARY CHEMICAL MICROSCOPY 
former motion. Complete the polishing with the finest washed 
and floated rouge, alumina, or emery kept well moistened upon 
soft and very close-textured broadcloth stretched upon a wooden 
lap. A beautiful mirror surface should have been obtained with 
no signs of striations when examined with a microscope of the 
same power as will be employed after etching. Wash the speci¬ 
men carefully, and dry by gently pressing with lens paper. 
Never ruh when drying and always avoid touching the polished 
surface with the unprotected fingers. 
If oil has been used as the vehicle, wash first with gasoline or 
benzene, and follow with alcohol and ether. 
General Methods for Preparing Soft Specimens. — The beginner 
should never attempt to grind and polish soft specimens upon a 
rotating wheel or lap. Even the roughing is best done with a 
file or by rubbing upon abrasive paper or cloth glued upon blocks 
of wood. Great care must be observed in rubbing the speci¬ 
men so that it shall never turn. The lines of abrasion must be 
kept parallel. Every few minutes the block should be turned 
on edge and struck upon the bench with a sharp blow in order 
to clear it from loose particles and dust; if this is not done deep 
scoring of the surface is sure to follow. When passing from one 
abrasive to a finer one, turn the specimen to a position at right 
angles to the other and rub very gently until every trace of the 
former scratches has disappeared. The polishing is carried out 
in the same manner upon close-textured soft cloth stretched 
upon blocks and covered with a thin paste of rouge or alumina, 
ending up with the finest possible floated rouge. It will be found 
convenient to pass from a grain of 220 to F, to FF, to FFF, then 
to fine rouge or emery and finally end up with the finest emery 
obtained as described above. Rouge usually causes a “ surface 
flow ” of the softer components. Wash, and dry the specimen 
with lens paper. But even lens paper will scratch the surface 
of soft alloys or other soft material. 
When dealing with very soft materials, after washing with 
water, shake off the last drops and pour absolute alcohol over the 
polished surface, shake, repeat the operation and then remove 
the last traces of alcohol with a few drops of ether. 
