112 GEORGE MERCER DAWSON ON THE 



metrically measured, is 1680 feet above the sea; others stand at esti- 

 mated heights of from 1780 to 1880 feet. Further up the Thompson a 

 terrace, again barometrically measured, was found at 1600 feet, and 

 a second, well denned, estimated at 1900 feet. These are no doubt 

 the same as the two last mentioned. On the Bonaparte river (tri- 

 butary to the Thompson), four miles north of Cache Creek, a terrace 

 estimated at 2820 feet occurs, and further on, at Maiden Creek, one 

 barometrically measured at 2680 feet. On ascending the plateau 

 beyond Clinton (already mentioned) ill-defined " Boulder-clay ter- 

 races " are seen, in some places, above 3000 feet*. On entering the 

 Thompson Yalley the material of the terraces becomes much finer 

 and more argillaceous than on the lower Eraser. In some places 

 several hundred feet of nearly horizontal clay beds are exposed in 

 transverse ravines, and seem to form the material of the terraces 

 running along the sides of the valley. The lower terraces, which 

 are always the best-preserved, are seen in many places to spread 

 quite widely, and their deposits (shown in sections both parallel and 

 transverse to the valley) to lie in beds nearly horizontal, or with a 

 slight sag towards the centre. Individual gravel beds can some- 

 times be traced in the banks for a mile or more. 



Carefully noting the aspect of the terraces in ascending the Eraser 

 and Thompson rivers, which flow in the main-drainage valley of the 

 great interior of British Columbia, tracing them from point to point 

 with scarcely any break, and upward to the higher streams and most 

 secluded nooks among the mountains, where denudation has been 

 least effective, the conclusion is forced on the mind, that, while many 

 of the higher are accumulations along the shore of a great sheet of 

 water, most of the lower have been carved out of deposits which at 

 one time filled the valleys from rim to rim, and more or less com- 

 pletely levelled up the broken surface of the country, by the gradu- 

 ally receding waters of a lake or of the sea, and eventually by the 

 rivers themselves deepening their channels to their old Preglacial 

 levels. 



Moraines. — In some cases it is not easy to distinguish between 

 certain fragments of high-level terraces and old lateral moraines. 

 Much doubt may also obtain with regard to the origin of moraine- 

 like forms when in the last stages of degradation from subsequent 

 water-action and subaerial decay. A further lifficulty is frequently 

 found in British Columbia in ridges simulating moraines, formed 

 where successive slides have taken place in great beds of drift- 

 deposits surrounding rivers and lakes. Disregarding, however, all 

 cases in which there can be the least doubt, there still remains 

 abundant evidence of the great extension of glaciers from the pre- 

 sent mountain -centres, and their sporadic appearance in many parts 

 of the highlands and hills of the plateau. These appear to be the 



* The terraces above enumerated occur in the vicinity of the main waggon - 

 road. The measurements lay no claim to accuracy, being in many cases merely 

 eye estimates aided by the known elevations of certain localities and the baro- 

 meter. They may serve, however, to show the succession met with in travel- 

 ling inland. 



