Hardcastle. — On the Drift in SoufJi Canicrhury. 321 



aud some of the streams near the coast are 40ft. to 50ft. thick, 

 whilst others quite thin out there. The volcanic display at 

 Geraldine was on a much smaller scale, and was limited to 

 the emission of lava. At all events, I could detect no tuff 

 beneath the rock where, on opposite sides of the field, the 

 base is exposed. The tvro lava-fields are about fifteen miles 

 apart at their nearest points. 



These two lava sheets have played an important part for 

 the geologist by preserving the land-surfaces of the time of the 

 eniption, while subsequent denudation has provided numerous 

 sections in which those surfaces can be studied. The com- 

 plete removal of a considerable quantity of rock" at the Timaru 

 Harbour Quarry gave an additional and excellent opportunity 

 for further observations on the tulf-covered soil. 



With an exception to be mentioned presently, the Timaru 

 dolerite seems everywhere to rest upon the red-gravel forma- 

 tion. At the coast and the Harbour Quarry the rock and its 

 underlying tuff rest upon a dark vegetable soil, containing 

 plant-remains in carbonized matter, and root marks ; also 

 worm-borings and bones of large birds. The tuff in places is 

 pierced with blackened tubes, the vestiges of culms of grasses, 

 aud black prints of leaves have been seen in it. The subsoil is 

 a gravelly clay, 1ft. to 2ft. deep, derived from decomposition 

 of shingle, and not to be mistaken for a deposited silt, as 

 pebbles are scattered at random through it to the very surface 

 of the soil, these being doubtless the more refractory pebbles 

 of the original shingle-bed. I have nowhere found a soil and 

 subsoil of this description within the red gravels. The marks 

 of r<^rsistent land-surfaces, previously mentioned, are in every 

 case in surfaces of beds of clay or silt, deposited as such. 

 (The bed of loam over which water drips, mentioned in Haast's 

 report as occurring in some of the terrace sections, may be a 

 soil of decomposition, a buried soil contemporary with that 

 entombed by the Timaru dolerite.) The soil disclosed by the 

 quarry-work at Timaru contains unmistakable worm-borings ; 

 but the fact that pebbles are found in the soil to the very 

 surface seems to indicate that the worms from first to last had 

 not been very numerous, as their operations tend to bury such 

 things. In one spot the Geraldine lava rests upon bare red 

 gravel, as though it here flowed over a watercourse swept 

 clear of recent shingle, and the lower side of the rock is 

 pecuharly splintered, as though it had flowed into water and 

 been suddenly cooled. Elsewhere this lava sheet is seen rest- 

 ing upon a dark soil derived from the red gravels beneath. At 

 one section the underside of the rock shows a semi-cylindrical 

 cavity, presenting the appearance it might do if the lava had 

 flowed over a prostrate log. I have nowhere found any signs 

 of timber beneath the Timaru dolerite, but I obtained, from 

 21 



