No. 7.J G. M. DAWSON — SURFACE GEOLOGY. 397 



complicated form on any good map will show ; nor do the circum- 

 Btances allow them to be accounted for by the excavating action 

 of systems of local glaciers. If, however, the Strait of Georgia 

 ice-sheet ever traversed the low country now occupied by the 

 Sound, it may have planed and levelled it to some extent. 



Mr. George Gibbs has described the passages and inlets of 

 Puget Sound as excavated in many places in drift deposits, 

 which appear not only to form their present banks, but to under- 

 lie their beds. Guided by the general form of the inlets, and 

 this description, I ventured in a note on some of the more recent 

 changes in level of the coast of British Columbia and adjacent 

 regions, printed in the Canadian Naturalist for 1877, to suggest 

 that they were cut out by rivers during a post-glacial elevation of 

 the land, and afterwards filled up by sea-water on its depres- 

 sion to the present level. 



Though aware of the danger of generalising hastily for a re- 

 gion which has not been thoroughly examined, I now venture to 

 again advance this idea with somewhat greater confidence. In 

 their outline on the map, these inlets resemble the fjords with 

 which the whole coast north of the forty- ninth parallel is dissected, 

 but the latter penetrate into the heart of a rugged and moun- 

 tainous country, and though they may have been cleared of drift 

 material during a post-glacial elevation, have probably been ex- 

 cavated in the hard rocks of the Coast Range of British Columbia 

 during a prolonged period in the later Tertiary, when the land 

 was at a high level. The canals of the Sound are excavated in a 

 low drift-encumbered country, based on soft Tertiary rocks, which, 

 owing to the thickness of later deposits are seldom seen. The 

 average height of the surrounding drift-plateau is from 180 to 

 200 feet. The channels are deep — often over 100 fathoms — but 

 not uniformly so, as shallower bars cross them in many places 

 which would give rise to a series of great lakes if reelevation 

 should now occur. Here bars, like those so often found near 

 the entrance of the fjords to the north, are generally in observable 

 connection with their cause, in the opposition of tidal currents, 

 the slackening of these currents as they enter wider channels, 

 or other circumstances bringing about the deposition of sus- 

 pended sediment. They are probably due to the most modern 

 period. In the wide flats surrounding the mouths of streams 

 and rivers, near the present water level, we have evidence of the 

 comparative permanence of the present relations of sea and land. 



