116 CKUISE OF THE NEPTUNE 



than these Silurian limestones are not found south of Lancaster 

 sound and Barrow strait, except on the northern part of Banks 

 island at the extreme west of the archipelago. These rocks of 

 Devonian and Carboniferous age occupy the Parry islands and 

 the western and northern parts of Ellesmere, and in many 

 places contain good deposits of coal. 



A yet newer series of rocks belonging to the Mesozoic are 

 found along the Avestern edge of Ellesmere and on the Sverdrup 

 islands. Isolated patches of later Tertiary age probably also 

 occur along the northern and eastern coasts of Baffin island, and 

 are of importance in that they are often associated with deposits 

 of lignite coal. Small areas of this age have been found in the 

 Parry islands and on the western part of Banks island. 



On these northern islands the country underlain by the crys- 

 talline Archaean rocks is very similar in physical character to 

 like areas of more southern regions. Where these rocks occur, 

 the coast is usually greatly broken by irregularly shaped bays 

 and headlands. The shores are often fringed with rocky 

 islands, and the adjacent sea-bottom is liable to be very uneven. 

 The land, as a rule, rises rapidly from the coast into an uneven 

 plateau or tableland, whose general level is broken by ridges of 

 rounded hills which seldom rise more than a few hundred feet 

 above the general level. The elevation of the tableland varies 

 from a few hundred feet to an extreme height of nearly five 

 thousand feet. 



In the northern parts the surface of this Archaean tableland 

 is usually covered with a thick ice-cap, through which only the 

 loftier hills protrude. The valleys leading down to the coast 

 from the ice-cap are filled with large glaciers which project into 

 the bays, where they discharge numerous icebergs. As the ice- 

 cap becomes thinner in the more southern parts the glaciers 

 become less active, and generally terminate without reach- 

 ing the sea, and consequently no icebergs are formed from 

 them. 





