300 THE POPULAR SCIENCE MONTHLY. 



THE SAND-BLAST. 



* 



By W. S. WAED. 



PROF. WILLIAM P. BLAKE, in a communication "On the 

 Grooving and Polishing of Hard Rocks and Minerals by Dry- 

 Sand," which appeared in the American Journal of IScievice and Arts, 

 September, 1855, describes the phenomena observed by him in 1838, 

 in the Pass of San Bernardino, California, as follows : " On the eastern 

 declivities of the pass, the side turned toward the desert, tlie granite 

 and associate rocks which form the sharp peak San Gorgonio extend 

 down the valley of the pass in a succession of sharp ridges, which, be- 

 ing devoid of soil and of vegetation, stand out in bold and rugged out- 

 lines against the clear, unclouded sky of that desert-region. It was 

 on these projecting spurs of San Gorgonio that the phenomena of 

 grooving were seen ; the whole surface of the granite over broad 

 spaces was cut into long and perfectly paralleltgrooves and little 

 furrows, and every portion of it was beautifully smoothed, and, 

 though very uneven, had a fine polish." While contemplating these 

 curious effects, the solution of the problem was presented. The wind 

 was blowing very hard, and carried with it numerous little grains of 

 sand. A closer examination disclosed the fact that the whole of the 

 polished surface was enveloped in an atmosphere of moving sand, and 

 it was through the grinding and rubbing of these minute but number- 

 less quartz-atoms that the rough surfaces of these rocks had been 

 made smooth, and the natural grooves deepened and polished. 

 " Even quartz," he observed, " was cut away and polished ; garnets 

 and tourmaline were also cut and left with polished surfaces. . . . 

 Whenever a garnet or a lump of quartz was imbedded in compact 

 feldspar and favorably presented to the action of the sand, the feld- 

 spar was cut away around the hard mineral, which was thus left 

 standing in relief above the general surface." 



The traveler whose good fortune it is to visit our Western wonder- 

 land, will note among the many fingers in his guide-book one pointing 

 in the direction of the now famous Monument Park. Entering a 

 narrow valley bordered by mountain-walls, he will find himself gazing 

 in wonderment at the rounded stone columns, rising about him in 

 groups or singly, to a height ranging from ten to forty feet, and in 

 many instances surmounted with grotesque cap-like coverings, that 

 rest balanced upon the frail pinnacles of the rock-columns. An in- 

 quiry as to the causes of their existence, standing as they do in isola- 

 tion on the surface of the valley low-lands, will elicit the reply that 

 they were made by the wearing ajvay of the surrounding rocks by 

 sand, which, whirling about in water or air eddies, acted like chisels 

 of the turner's lathe. Where the depressions were deepest there the 



