418 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1936 



placed, the depth of the cut of the figures or the kind of pigment 

 used, and the exposure to sun, rain, and blown sand. Painted petro- 

 glyplis in caves of Europe have lasted nearly 25,000 years ; in exposed 

 places in America, some have practically disappeared within 50 years. 

 Although degree of weathering may sometimes provide a clue as to 

 age, it is never conclusive. 



In some areas it is possible provisionally to relate petroglyphs to 

 known cultural horizons by comparing the subjects and art styles 



-^ ui 





J k / 



FiGUBH 4. — Petroglyphs representing mythical or imaginary beings, a. Little Indian Rock, 

 Pa. ; 6, Safe Harbor, Pa. ; c. Clear Creek, Utah ; d, near Blairsdeu, Calif. ; e, figure in 

 Tulare County, Calif. ; f. The Dalles, Columbia River ; fir to i, N. Mex. e is painted red ; 

 the others are carved. 



of the former with those of objects dug from the ground. Thus 

 when rock designs closely resemble those on a certain type of pot- 

 tery (e. g., pi. 6), it is reasonably certain that the two were made by 

 the same people. Evidence of this kind is more fully discussed 

 below. There are, however, many dangers of misinterpreting these 

 similarities. This method, though one of the most promising, must 

 be carried out in much greater detail before its results will be 

 satisfactory. 



Now and then it is claimed that some petroglyph represents a 

 now extinct species of animal. When it is asserted, as in Arizona 



