The bold and not deeply sculptured mountains along the nearly unbroken coast from the Strait of Fuca to Panama, rise close to the true border of the continent. The continental shelf of this portion of the shore of the Pacific is narrow. An elevation of 100 fathoms would add scarcely more than 10 miles to the extent of the land. This narrowness of the continental shelf seems to be due to the recency of the uplifting of the Coast mountains, and the lack of time for the _debris_ from the land and the organic refuse of the sea to shoal the water. The Pacific basin is deep close to the land bordering it, thus restricting the seaward extension of the continental shelf. _Changes in the Coast-Line due to Ice._--It is now well known that glacial ice many hundreds of feet thick formerly covered the northern half of North America and flowed outward across the present position of the coast-line throughout all of the northern border of the continent from Staten Island in the east and Puget Sound in the west, with the exception of the Arctic and Bering Sea coasts of Alaska. The effects of this outward-flowing ice on the topography of the continental border crossed by it were in general in two directions. Where the land was rough or moderately so previous to the coming of the ice-sheets the inequalities of surface were increased; but where the land was smooth or but gently undulating its elevations were planed away by the glaciers and made still more smooth. The reason for these differences is that when the land from which the ice flowed was rugged or had previously been deeply trenched by streams, the valleys gave direction to the ice currents and the margins of the continental ice-sheets became divided into separate ice-streams, as is the case in Greenland at the present day. This localization of the ice currents served to deepen and broaden the pre-existing valleys, and especially on the bold coast of Alaska and British Columbia increased in a marked way the inequalities of the surface and favoured the production of a ragged coast-line when the ice melted and was replaced in part by the sea. When, however, the topography of the land was not sufficiently accented to cause the ice flowing over it to gather into well-defined currents the general surface was worn down, thus favouring the production of an even coast-line after the melting of the ice-sheets.