Kev. J. Brodie on Level Terraces, 339 



the wind, the level can be easily traced. The shingle either 

 remains altogether bare, or is covered with only a few inches 

 of sandy soil. When, along with the gravel, there is a small 

 quantity of sand, not sufficient to bury beneath it the grass 

 and other plants that grow in such situations, we find, it may 

 be, several feet of soil covering the shingle and forming a 

 surface, which may be termed level, though the uniformity 

 be broken by a number of small irregularities. When the 

 quantity of sand is great, it is formed by the force of the 

 wind into hillocks of considerable height, and is sometimes 

 spread over a large extent of ground. Tradition, for ex- 

 ample, says that the sand thrown up by the sea in one terrible 

 storm on the coast of Aberdeenshire, was so great that, 

 when afterwards drifted by the wind, it covered over a 

 whole parish in the neighbourhood of Slains. A great pro- 

 portion of what are called downs in England and links in 

 Scotland seem to have been formed in this manner. They 

 are terraces thrown up by the advancing billow, and after- 

 wards covered by a varying depth of sand. In estuaries 

 the material thrown up consists principally of mud, which 

 hardens when dry, and is not so readily blown about by the 

 wind. After it has been thrown up it settles down upon the 

 roots of whatever plants may be growing on the shore, 

 and promotes their increase. By this means it is evenly 

 spread over the surface, and forms the rich alluvial soil 

 which we sometimes find on the plains that border the 

 mouths of rivers. The lower terraces formed under the 

 water by the retreating wave do not in general possess a 

 horizontality of surface so distinctly marked as that which 

 we find in those that are formed above high-water mark by 

 the advancing billow. There is no doubt that the agency 

 of the waves, if it acted alone, would produce a level plat- 

 form below the water, as well as one above it ; but wherever 

 there are currents, the material, carried into the deeper 

 water by the retreating wave, is swept before them, and 

 thrown up into banks of very irregular height. In lakes and 

 seas, where there is neither stream nor tide, and in land- 

 locked gulfs, where the movements usually found in the 

 ocean have little influence, a level terrace under the water 



