54 PICTURE-WRITING OF THE AMERICAN INDIANS. 
“The drawings were outlined by pecking with a piece of quartz or other 
siliceous rock, the depth varying from a mere visible depression to a 
third of an inch. Having thus satisfactorily depicted the several ideas, 
colors were applied which appear to have penetrated the slight inter- 
stices between the crystalline particles of the rock, which had been 
bruised and slightly fractured by hammering with a piece of stone. It 
appears probable, too, that to insure better results the hammering was 
repeated after application of the colors. 
“Upon a small bowlder, under the natural archway formed by the 
breaking of the large rock, small depressions were found which had 
been used as mortars for grinding and mixing the colors. These de- 
pressions average 2 inches in diameter and about 1 inch in depth. 
Fig, 12.—Petroglyph at Tule river, California. 
Traces of color still remain, mixed with a thin layer of a shining sub- 
stance resembling a coating of varnish and of flinty hardness. This 
coating is so thin that it can not be removed with a steel instrument, 
and appears to have become a part of the rock itself. 
“From the animals depicted upon the ceiling it seems that both beaver 
and deer were found in the country, and as the beaver tail and the hoofs 
of deer and antelope are boiled to procure glue, it is probable that the 
tribe which made these pictographs was as far advanced in respect to 
the making of glue and preparing of paints as most other tribes through- 
out the United States. 
“ Wxamination shows that the dull red color is red ocher, found in vari- 
