Canterbury and Westland. 301 



compact and fine-grained, than the streams which have a more 

 porphyritic structure ; besides the example just given, the dolerites in 

 the Acheron show this difference very conspicuously. The felspar in 

 some of these latter beds is most probably nepheline. Another series 

 here to be considered is the youngest. It occurs all along the eastern 

 side of the district, forming large sheets of doleritic rocks, which have 

 flowed over the bottom of the sea, and afterwards, when being raised to 

 form subaerial hills, have protected the beds of loose quartzose sands 

 below them. There are several streams, mostly close together, which 

 in the Harper's hills and the Dean's range show all their characteristic 

 features. The first stream flowing over the sands has generally had a 

 vitrifying influence ; the sands have been melted for a few inches, or even 

 one foot, and have been changed into a flint-like rock. In other localities 

 doleritic tufas overlying the sands have protected them so effectually, 

 that no change is visible. Between the lava-streams, having a thickness 

 varying from a few feet to nearly 100 feet, sometimes, layers of 

 pitchopal occur, often enclosing stems and leaves of plants ; in some 

 other localities palagonite tufas have been formed. The basic rocks 

 under review have the peculiar character to which the name of 

 anamesite has been given by Leonhard, some of them are scoriaceous, 

 having the vesicular cavities lined with sphserosiderite. The latter 

 variety would offer good material for mill stones, a similar rock being 

 extensively used on the continent of Europe for that purpose. 



It might perhaps be useful if I allude here to the various charac- 

 teristic features and age of these different basic rocks, which have 

 during that whole period made their appearance, and through which some 

 important changes have taken place in that district. There are three 

 important divisions in the basic or basaltic rocks appearing during 

 this geological period in that part of New Zealand : — Eirst. — Rocks 

 coeval with or even prior to the formation of the principal Brown 

 coal beds, the latter having been altered effectually, both vertically 

 and horizontally, by the former. Second. — Rocks appearing only after 

 the deposition of the calcareous f ossilif erous beds overlying the Brown 

 coal series, or even after the formation of the greensands. Third. — 

 Rocks of which the extensive streams of anamesite consist, forming a 

 well defined horizon, and closing an important geological epoch in the 

 district. The rocks of the first division are very peculiar. They have 

 a dark greenish colour, are granular, and resemble in hand specimens 

 some eruptive (diabasic) rocks of older origin. Some of them 

 have the peculiar greenish tint which an admixture of chlorite 

 usually gives, although I do not think it exists in them. 



