THE 



GEOLOGICAL MAGAZINE. 



NEW SERIES. DECADE IV. VOL. VIII. 



No. v.— MAY, 1901. 



I. — Sand-blast of the Shoee and its Erosive Effect on Wood. 

 By T. Mellard Re.-vde, C.E., F.G.S., F.R.I.B.A. 

 (PLATE X.) 



1MLE effect of the natural sand-blast of the desert in eroding soft 

 and hard rock has long been known, and attracted much 

 attention, but I cannot call to mind any account of the effect of 

 blowing sand impinging upon wood. 



From seven to eight years ago a boat-house was built b}' the 

 Blundellsands Sailing Club on the sandhills at the Altmouth, about 

 8 or 9 feet above high- water mai*k of spring tides. Afterwards, for 

 better access thereto, a sloped road was built up of timbers from the 

 shore level, leading to a level gangway about 10 feet above the shore, 

 also made of timbers. This gangway was 6 feet wide and 12 feet 

 long, with close-boarded sides about 2 feet high formed of roughly 

 sawn pine boards and split-oak staves. This formed a trough having 

 a direction about west-north-west, and really became a wind-gap. 



The effect of the sand-blast on the southern face of the northern 

 side has been most striking and curious. The boat-house has just 

 been taken down and re-erected at a lower level, and my sons, 

 members of the club, have brought me a sample of the pine boarding 

 and of the split-oak staves from the north side of the old gangway. 

 These are reproduced in the Plate from photographs by Hartley Bros., 

 Waterloo. The general effect of the sand-blast has been to remove 

 from one-eighth to three-sixteenths of an inch of wood over a large 

 part of the surface of the pine board (PI. X, Fig. 1). and to develop 

 the structure of the wood in a remarkable manner. The grain being 

 very irregular, the differential effect of the impinging sand-grains 

 on the harder and softer portions is most instructive. 



It will be observed that the large hard knot stands out above the 

 general surface of the wood, and that the grain around the knot is 

 picked out in a surprising manner. The knot itself is carved and 

 polished. Perhaps the most instructive feature is ilwr^fffeet t>f-Uie 



DECAT)E IV. — VOL. VIII. — NO. V. r/^^* 1'^ 'Co \\ 



