420 Prof. G. H. Stone—Stones of the Salt Range. 
scratches that can be distinguished by the unassisted eye, but they are 
seldom more than a small fraction of an inch in length. Here, in the 
Rocky Mountains, the finer dust broadens these larger scratches more 
. than it deepens them, so that they are soon obliterated or changed to 
shallow grooves. Stones one-fourth to half an inch in diameter are 
frequently transported by the winter winds, and the flying gravel is 
sometimes so painful that hcrses cannot be made to face it, and I 
know of a blue eye-shade that was broken by gravel while the 
wearer was facing a Chinook wind in Colorado. 
Now the scratches of these Salt Range stones have sharply-defined 
borders, and they are two inches or somewhat less in length, and 
most of them very straight. The graving tools that produced them 
moved with a very steady motion, and the depth is such, that a 
considerable force was required. The hypothesis that under any 
conditions blowing sand or gravel could produce such scratches may 
once for all be confidently rejected. 
Fourth.—Assuming that the scratching could not be caused by 
wind action, could the facetting be so caused ? 
We may classify with sufficient accuracy for our present purpose 
the conditions under which facetting is done by the wind as follows. 
First, where the upper surface of a stone only a few inches in 
diameter lies nearly on the same level as the surface of the soil 
or of other stones around it. The small stone often has its upper 
surface ground away to near the level of the adjacent earth, 
and often has its form determined by the shape of the adjoining 
bodies. It is surprising how flat many of these small facets are, 
especially when the stone is homogeneous in composition. Examina- 
tion of many facets shows a tendency to form a gently undulating 
surface, the crests of the low undulations more often being transverse 
to the direction of the wind and an inch or more apart. In the 
class under consideration the stone is so small, and is so far protected 
by the adjacent bodies, that a large part of the carving is done by 
flying grains as they first strike the stone. at which time their 
motion had been in great measure determined by the adjacent land 
surface. 
If in any way one of these small stones becomes overturned, a new 
facet may be formed in the same manner. 
A somewhat different case is presented when a stone or boulder 
projects considerably above the ground, or has a large and nearly 
horizontal surface near the ground. In this case a much larger 
proportion of the grinding is done after the blowing stones have 
once rebounded from the fixed stone. The rhythmical friction of 
the wind against the fixed stone and the repeated reboundings 
in this case determine the character of the carving more than the 
direction of original impact. The sand-carved surface under these 
circumstances is usually covered by shallow grooves parallel with 
the direction of the prevailing wind. This form of carving appears 
to be related to the oblique reboundings of the grains sidewise. 
The grooves are an inch or less in breadth and seldom more than 
the sixteenth of an inch in depth. The difference between the two 
