Cockayne. — Plant Geography of the Waimakariri. 103 



described more fully when treating of their very peculiar and 

 amazing plants. 



The surface of the table-land consists of fluviatile and 

 glacial deposits, covered often with a very scanty alluvial soil, 

 below the general level of which the rivers meander in several 

 streams over wide stony beds, with huge terraces, sometimes 

 four in number, on either side. 



The Trelissick basin has been examined in a thorough 

 manner by Captain Hutton,''' and so the relation between the 

 soil and its plant-covering can be there better studied than in 

 any other part of the district. The sections shown in pi. xxv. 

 are of great importance for this purpose. The Trelissick 

 basin consists of undulating country, rising in places to a 

 height of 900 m., and formed of rocks belonging to — the 

 Pareora system (Miocene), a series of blue clays, shales, and 

 sandstones; the Oamaru system (Oligocene), consisting of 

 coralline limestone, underlain by volcanic grits and tuffs ; 

 the Waipara system (Cretaceous), formed of argillaceous 

 limestone and calcareous sandstone underlain by marl. In 

 addition to these are to be found some brown-coal beds to- 

 wards the northern extremity of Mount Torlesse, at the base 

 of the Craigieburn Mountains, in the Craigieburn Creek, and 

 elsewhere. In the Esk Valley there is also a small tract of 

 limestone country, which is described by Haast iloc. cit., 

 p. 151) as consisting of " younger outliers of greensand and 

 calcareous limestone, which have been broken through and 

 covered with dolerites, to the hard nature of which they 

 doubtless owe their preservation during the great Ice age." 



Leaving the mountain region and coming to the Canter- 

 bury Plain, it is seen to be formed of stony debris brought 

 down by the rivers from the neighbouring mountains. Its flat 

 monotony is slightly relieved at its upper end by several low 

 hills named respectively Racecourse Hill, Little Racecourse 

 Hill, Gorge Hill, View Hill, and Burnt Hill. Of these the 

 two latter owe their importance to the fact of the rocks con- 

 sisting of basalt and dolerites ; Gorge Hill belongs, on the 

 other hand, to the Mount Torlesse formation, already men- 

 tioned ; while Racecourse and Little Racecourse Hills consist 

 of shingle. 



At about four miles from the sea the sand-dunes are en- 

 countered—at first ancient dunes, which are separated from 

 the more recent by stretches of low-lying swampy land. 

 These sandhills are formed by the sand blowing inland from 

 the seashore during the frequent and persistent east winds, 

 while the heavy north-west and south-west (if dry) gales blow 

 back again to the shore large quantities of sand, often chang- 

 ing more or less the aspect of the scene. 



* Trans. N.Z. Inst., vol. xix., p. 415. 



