Page:Popular Science Monthly Volume 8.djvu/315

Rh rocky strata were soft and yielding, and were the more readily cut away; but where the opposing surface was hard, as in the case of the black cap-pieces, the action was less rapid, and the reduction of the rock less decided. Glancing off from these, the whole force of the driving sand was projected against the strata immediately below, thus reducing it in size till there seems hardly circumference enough left to sustain the weight above.



So much for the observations of the geologist and explorer, made nearly half a century ago, and placed on record as forming but one of the many startling features of that wonderful region, but suggesting to the traveler little else than a reasonable theory by which to account for a hitherto mysterious class of physical phenomena. From this, the record of the student of Nature, we turn to a second record, more practical in character, and having a direct bearing upon the subject under review.

Whether the author or inventor of the modern sand-blast deserves any less credit for having had his idea anticipated in the workshops