THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



NOVEMBER 1873. 



XLII. On the Action of a Blast of Sand in cutting hard Material. 

 By Professor Osborne Reynolds, M.A.* 



MR. TILGHMAN has discovered that sand will, when 

 blown against any hard body, rapidly wear it away — that 

 it acts in what may be called a systematic and not merely in a 

 casual manner (that is to say, each grain produces its effect, and 

 not merely one grain here and there just scratches the surface) — - 

 that the material of the sand is not necessarily harder than the 

 material acted upon, but that the hardest bodies, such as steel 

 files and diamond, maybe cut by common sand or even by small 

 leaden shot — that it is not necessary that the grains of sand 

 should be of any particular size, the smaller grains producing 

 apparently the same effect as the larger — and that the velocity 

 with which the sand must be driven is after all nothing very 

 considerable, that for glass a velocity of 50 feet per second is 

 sufficient. 



Now these facts, in addition to their value from a useful point 

 of view, serve a scientific purpose, inasmuch as they call our 

 attention to circumstances of impact which have hitherto passed 

 unnoticed. When once our attention is called to them, we can 

 see that these circumstances have been before us in a variety 

 of shapes, and that they play a very important part in many 

 mechanical phenomena, but never till now have they taken a 

 shape sufficiently definite to compel attention. 



That one hard body will, when driven with sufficient velocity, 



* Communicated by the Author, having been read before Section A 

 of the British Association, September 1873. 



Phil. Mag. S. 4. Vol. 46. No. 307. Nov. 1873. 2 A 



