1871.] 149 [Kneeland. 



which he had already furnished to Count Pourtales for inves- 

 tigation. 



Dr. Kneeland exhibited several specimens of glass, marble and 

 hard stones, engraved, carved, and grooved by the action of sand 

 driven by a blast of air or steam. The surface being covered by 

 perforated paper or a stencil plate, the parts exposed by the perfora- 

 tions are cut rapidly and accurately, while the covered parts are un- 

 touched, protected, it is supposed, by the elasticity of the paper or 

 thin metal. 



He drew attention to this industrial process as illustrating the ad- 

 vantage of diffusing, as a common branch of knowledge, information 

 on the forces of nature, and, in this instance, on dynamical geology. 

 This process, which promises to revolutionize one of the most exten- 

 sive of the industrial arts, is simply carrying out what natural forces 

 have been doing to the surface rocks of our continent for ages. 



Sands carried by strong and steady winds, passing over rocks, often 

 wear them smooth or cover them with grooves and scratches, as no- 

 ticed and figured by Mr. Blake, in the granite rocks at San Bernar- 

 dino Pass, Cal. : see Pacific R. R. Reports, vol. V, pp. 92 and 231. 

 Quartz rocks were there found polished, the softer felspar being cut 

 away; where the latter had been protected by garnets, projections 

 were left, tipped with the hard garnets, pointing like fingers in the 

 direction of the wind. On the surface of the great Colorado desert 

 the pebbles are finely polished by the drifting sand, or variously 

 grooved, according to the hardness of their substance. Prof. J. 

 Wyman also mentions that glass windows on Cape Cod have some- 

 times holes worn in them by the drifting sands blown by the winds. 



It is the tendency of modern education to pay less attention to the 

 dead languages and to ancient history, as a means of culture, and 

 more to the practical and living issues of the day, and especially to 

 combine a knowledge of natural phenomena with the elementary in- 

 struction of the school room. In this particular instance, it is 

 altogether probable that, if the grooving of rocks by the wind-driven 

 sands, long known by geologists and physicists, and by them turned 

 to no practical account, had been equally well known to our intelli- 

 gent and skilful mechanics, the process here illustrated would have 

 been invented years ago, and by this time have attained a high de- 

 gree of perfection. The same reasoning will apply to other depart- 

 ments of natural and physical science, and goes to show the wisdom 



