34 PICTURE-WRITING OF THE AMERICAN INDIANS. 
seem to involve details of wharfing, staging, and ladders if operated 
from the base, and no less elaborate machinery if approached from the 
summit. Strahlenberg suggests that such elevated drawings were 
made by the ingenious use of stone wedges driven into the rock, thus 
affording support for ascent or descent, and reports that he actually 
saw such stone wedges in position on the Yenesei river. A very 
rough geological theory has been presented by others to account for 
the phenomena by the rise of the rocks to a height far above the ad- 
jacent surface at a time later than their carving. 
But in the many cases observed in America it is not necessary to 
propose either the hypothesis involving such elaborate work as is sug- 
gested or one postulating enormous geological changes. The escarp- 
ment of cliffs is from time to time broken down by the action of the 
elements and the fragments fall to the base, frequently forming a talus 
of considerable height, on which it is easy to mount and incise or paint on 
the remaining perpendicular face of the cliff. When the latter adjoins 
a lake or large stream, the disintegrated débris is almost immediately 
carried off, leaving the drawings or paintings at an apparently inacces- 
sible altitude. When the cliff is on dry land, the rain, which is driven 
against the face of the cliff and thereby increased in volume and force 
at the point in question, also sweeps away the talus, though more 
slowly. The talus is ephemeral in all cases, and the face of the cliff 
may change in a week or a century, as it may happen, so its aspect 
gives but a slight evidence ef age. The presence, therefore, of the 
pictures on the heights described proves neither extraordinary skill m 
their maker nor the great antiquity which would be indicated by the 
emergence of the pictured rocks through volcanic or other dynamic 
agency. The age of the paintings and sculptures must be inferred from 
other considerations. 
Pictures are sometimes found on the parts of rocks which at present 
are always, or nearly always, covered with water. On the sea shore at 
Machias bay, Maine, the peckings have been continued below the line 
of the lowest tides as known during the present generation. In such 
cases subsidencesof the rocky formation may be indicated. At Kejim- 
koojik lake, Nova Scotia, incisions of the same character as those on 
the bare surface of the slate rocks can now be seen only by the aid of 
a water glass, and then only when the lake is at its lowest. This may 
be caused by subsidence of the rocks or by rise of the water through 
the substantial damming of the outlet. Some rocks on the shores of 
rivers, e. g., those on the Kanahwa, in West Virginia, show the same 
general result of the covering and concealment of petroglyphs by water, 
except in an unusual drought, which may more reasonably be attrib- 
uted to the gradual elevation of the river through the rise of the sur- 
face near its mouth than to the subsidence of the earth’s crust at the 
locality of the pictured rocks. 
It must be admitted that no hermeneutic key has been discovered 
