Speight. — Terrace-development of Canterbury Rivers. 31 



■due to elevation and to larger collecting-grounds, the proved 

 elevation of 600 ft. would cause a marked glacier extension ; it 

 might even cause a glacier epoch. Captain Hutton has previously 

 explained the advance of the glaciers as due to increased height 

 of the land, and pointed out, from biological evidence, that there 

 could have been no marked refrigeration of the climate. 



Another effect of elevation of the land would be to cause 

 desert or steppe conditions to prevail on the plains at the foot 

 of the mountains. Owing to their increased height, the mountains 

 would intercept more of the moisture brought by prevaibng 

 westerly winds from the Tasman Sea, which, owing to its depth, 

 probably existed under the same conditions then as now. The 

 mountains would then intercept more moisture, and cause it to 

 fall as snow on the higher levels. Their eastern slopes near 

 Mount Hutt and Mount Torlesse receive their chief rainfall 

 from the west ; but, when the higher central ranges cut off this 

 moisture, the eastern slopes would receive much less of this 

 westerly rain. Further, owing to the coast-line being so far 

 to the east of its present position, there would be on the plains 

 a smaller rainfall from the prevailing winds which at present 

 supply the coastal lands. Even at the present time the plains 

 of Canterbury experience a modified steppe climate. The average 

 rainfall for Hokitika is about 119 in. per year, while at Lincoln, 

 near the eastern border of the Canterbury Plains, it is only 

 25 in., and in one year it fell as low as 14 in. The average 

 annual rainfall for Christchurch is only 23 in. These steppe 

 conditions would be intensified during a period of elevation, 

 and the climate would resemble that of Patagonia or Thibet 

 as it is at present. 



The present steppe conditions are marked by the great 

 number of xerophilous plants which are found in Canterbury 

 and Otago, and there are indications from their life history 

 that the desert conditions were at one time more severe. 



In his admirable paper on the " Plant Geography of the 

 Waimakariri," Dr. Cockayne draws special attention to the 

 present climatic conditions of the country, and emphasizes the 

 existence of steppe conditions. When speaking of the eastern 

 climatic plant-region he says, " The cecological condition of 

 this region is essentially xerophilous. This is not to be wondered 

 at when the small rainfall and constant drying winds in con- 

 junction with the usually stony soil is considered." In this 

 same pap?r, in giving expression to an opinion of Diels, the 

 great cecological and systematic botanist, he further says, 

 '' Diels was much struck with the extreme xerophilous character 

 ■of many plants, which he considered out of all proportion to 

 any severity of climate they have now to endure. At the present 



