822 THE GEOGRAPHICAL SIGNIFICANCE OF FLOODS, 



Zealand, while the fiord-region gets from 150 to 250 inches of 

 moisture per annum, Lakes Wakatipu and Te Anau probably do 

 not exceed 60 inches. A comparable precipitation probably 

 obtained in the Ice Age, since no earth-movements of note 

 appear to have taken place here in postglacial time. 



2. Sierras . — A magnificent set of photographs illustrating 

 geographic contours in the Canadian Rockies has been presented 

 to the writer by A. O, Wheeler, of Calgary: and these shew 

 forms identical with New Zealand Alpine types. 



It is more than possible that the grand canon-contours of the 

 Sierras are associated with marked canon-convergences, or that 

 basins (lakes) have been formed by corrasion at marked conver- 

 gences, and lengthened by gravitative thrust of the upstream 

 glacier in its attempts to harmonise the canon-grades. Hanging- 

 valleys, sheer precipices and spurs shrivelled up to the main 

 canon-wall should be studied in connection with known direction 

 of resultant thrusts from canon-convergences. Lake Chelan 

 appears to be a remarkable study in structural strength, allowing 

 of profound preglacial narrows; of caiion-convergences with trough 

 (lake) development by reason of headward retreat of heavy ice- 

 falls initiated by some downstream canon-convergence. Mono 

 Lake region also appears to be a study in resistance or differential 

 strength. 



Cirques, also, probably arise in the main from the plunging 

 action of floods, as exemplified by ordinary stream-action. 

 Associated cols, when present, should always be examined in this 

 connection to discover the catchment area really belonging to a 

 canon during the Glacial Period. Willard D. Johnson, however, 

 in a brilliant note (19), suggests that cirque-corrasion is progress- 

 ing now along lines "curving sympathetically" with the 

 bergschrund. All such localities should be studied in connection 

 with the provisions of the Ice-Flood Hypothesis. 



One point which must not be lost sight of in this glacial study 

 is, that intense ice-action, as water-action, is extremely localised. 

 More misconceptions appear to have arisen from an oversight of 

 this fact than any other. With streams seeking the baselevel. 



