MALLERY.] SUGGESTIONS TO OBSERVERS. 715 
As a small drawing of large rock inscriptions must leave in doubt 
the degree of its finish and perhaps the essential objects of its pro- 
duction, it is requisite, in every instance, to affix the scale of the draw- 
ing, or to give a principal dimension to serve as a guide. A conven- 
ient scale for ordinary petroglyphs is one-sixteenth of actual size. The 
copy Should be with sufficient detail to show the character of the work. 
It is useful to show the lithologic character of the rock or bowlder 
used; whether the drawing has been scratched into the face of the rock, 
or incised more deeply with a sharp implement, and the depth of 
such incision; whether the design is merely outlined, or the whole 
body of the figures pecked out, and whether paint has been applied to 
the pecked surface, or the design executed with paint only. The com- 
position of paint should be ascertained when possible. The amount of 
weathering or erosion, together with the exposure, or any other fea- 
ture bearing on the question of antiquity, might prove important. If 
actual colors are not accessible for representation the ordinary heraldic 
scheme of colors can be used. 
That sketches, even by artists of ability, are not of high value in 
accuracy, is shown by the discrepant copies of some of the most care- 
fully studied pictographs, which discrepancies sometimes leave in 
uncertainty the points most needed for interpretation. Sketches, or 
still better, photographs are desirable to present a connected and gen- 
eral view of the characters and the surface upon which they are found. 
For accuracy of details ‘‘squeezes” should be obtained when practicable. 
A simple method of obtaining squeezes of petroglyphs, when the lines 
are sufficiently deep to receive an impression, is to take ordinary manilla 
paper of loose texture, and to spread the sheet, after being thoroughly 
wetted, over the surface, commencing at the top. The top edge may 
be temporarily secured by a small streak of starch or flour paste. The 
paper is then pressed upon the surface of the rock by means of a soft 
bristle brush, so that its texture is gently forced into every depression. 
Torn portions of the paper may be supplied by applying small patches 
of wet paper until every opening is thoroughly covered. A coating of 
ordinary paste, as above mentioned, is now applied to the entire sur- 
face, and a new sheet of paper, similarly softened by water, is laid over 
this and pressed down with the brush. This process is continued until 
three or four thicknesses of paper have been used. Upon drying, the 
entire mold will usually fall off by contraction. The edge at the top, 
if previously pasted to the rock, should be cut. The entire sheet can 
then be rolled up, or if inconveniently large can be cut in sections and 
properly marked for future purposes. This process yields the nega- 
tive. To obtain the positive the inner coating of the negative may be 
oiled, and the former process renewed upon the cast. 
The characters when painted with bright tints and upon a light- 
colored surface, may readily be traced upon tracing linen, such as is 
employed by topographers. Should the rock be of a dark color, and 
the characters indistinct, a simple process is to first follow the charac- 
