THE GEOLOGY OF THE ARCTIC COASTS. 565 



now going on in temperate climes. On the first signs of thaw large 

 masses of rock, separating along lines of weakness formed by planes 

 of jointing and bedding, are detached from the cliff, and falling on 

 the " screes," slide down to the ice-foot beneath, the impetus being 

 often sufficient to carry them on to the floe, where they remain until 

 the general break up of the ice, when vast quantities of material are 

 drifted seaward. 



The ice-foot appears to be formed not so much by the act of 

 freezing of the sea- water in contact with the coast, as by the accu- 

 mulation of the autumn snow-fall, which, as it drifts to the beach, 

 is met by the sea- water at a temperature just below the point of 

 freezing of fresh water, and instantaneously converted into ice, form- 

 ing a solid wall from the bottom of the sea. This wall is constantly 

 increasing in height from snow-falls. When the young ice or 

 " season floe" is formed at the surface of the sea adjacent to the ice- 

 foot, there is little difference between the level of the floe and the 

 ice-foot; but as the latter is constantly increasing in height, and 

 the former is twice daily oscillating with the change of tides, it is 

 easy to see how a line of junction is impossible ; and the height of 

 the surface of the ice-foot above the level of high water is mainly 

 dependent on the amount of snow-fall, while its depth below that 

 level is dependent upon the slope of the sea-bottom and the vertical 

 range of the tides. It is almost needless to observe that on exposed 

 and projecting headlands the ice-foot, like the beaches of temperate 

 regions, is invariably absent. 



It is not, however, until near the close of the thaw episode that 

 the ice-foot is discovered to be the cause of the production of the 

 remarkable terraces to which we have alluded. 



The typical aspect of the ice-foot in Smith Sound is that of a 

 terrace of fifty to a hundred yards in width, stretching from the base 

 of the " scree " to the water's edge, its width varying with the slope 

 of the sea-bottom, decreasing in direct proportion to the increase 

 of the land slope. 



The first action of the solar rays is exerted on the snow forming 

 the uppermost layer of the ice-foot which lies nearest to and upon 

 the talus or " screes," the dark surfaces of which rapidly absorb the 

 heat of the sun. A deep trench is formed at the junction, which 

 becomes filled with water, partly derived from the melted snow of 

 the ice-foot and partly from that pouring down from the uplands ; 

 these united streams in a few hours eat deep channels across the 

 ice-foot and discharge themselves into the sea through transverse 

 gullies, often exposing the underlying talus, and more rarely the 

 subjacent rock. At low water the ditches and gullies are drained, 

 whilst at high water the sea pours in through these apertures with 

 considerable violence, and sweeping right and left, traverses the 

 ditch, eats away the base of the talus, and reassorts the material. 



As the progressive elevation of the coast of Grinnell Land con- 

 tinues, degradation of the older terraces ensues, and the materials 

 of which they are composed are shifted to lower levels, and go to 

 make up the terraces now in process of formation. 



Where degradation has been excessive all traces of older terracos 



