202 A NEW ZEALAND NATURALIST'S CALENDAR. 



columnar structure on the sea-face, while the superficial 

 portions are often highly vesicular. A very short distance 

 down the coast and we find the basalt running out, and 

 can see that it overlies the massive strata of nearly level- 

 bedded sandstone. This latter is a marine formation, 

 containing shells, and takes us back to a period antecedent 

 to that in which volcanic action became so pronounced in 

 this neighbourhood. Our course along the water-parting 

 takes us over this bed of sandstone till we approach Morn- 

 ington, when again we pass on to the basalt. There is one 

 considerable area of clay here, at a height of about 450 

 feet above the sea, which Captain Hutton considers to be of 

 pleistocene age. As this rests on the top of the volcanic 

 rocks it implies a very great subsidence in recent geological 

 times, and although other beds of apparently similar age 

 occur in other parts of Otago, along the east coast, it is 

 rather remarkable that this isolated patch should be the 

 only one occurring in this immediate neighbourhood. 



The narrow crest of the ridge between Mornington and 

 Roslyn rises in the latter suburb to a height of over 700 

 feet, and then dips steadily to the brow of Maori Hill, 

 where it ends abruptly in basaltic cliffs some 200 feet or so 

 above sea-level. But the tmdei'lying rock is not of uniform 

 material throughout. A little to the north of the line of 

 Ross Street in Roslyn there is a change in the formation. 

 To the south-west of this line the superficial beds appear to 

 consist of lava flows of very vesicular basalt with what I 

 take to be beds of volcanic ash, all so porous that water 

 cannot be got by sinking wells, and which weathers to a 

 warm, friable, dark red (ferruginous) soil. To the north- 

 east of this line of demarcation there is a colder more 

 hungry soil with a retentive clay subsoil in which springs 

 occur, and which before the days of close settlement 

 yielded wells of good water. This soil is improved by 

 liberal applications of lime, and is altogether less satis- 

 factory to cultivate than the other. The transition from 

 the one to the other soil is again readily seen on the road 

 between Balmacewen and Halfway Bush, where one passes 

 from the cold clay to a bed of volcanic ash or weathered 



