370 Transactions. —Geology. 



which is quoted on page 300 of Haast's " Geology of Westland 

 and Canterbury." Subsequently the rock was examined by 

 Professor Ulrich, and he discovered the rare mineral tridymite 

 in it. Specimens were also sent to Professor Von Eath, but 

 no detailed description of the rock has yet been published, 

 though a collection of volcanic rocks was described in Ger- 

 many. 



Professor Von Haast, in the " Geology of Canterbury and 

 Westland," describes this rock as "a remarkable trachyte 

 rock, interstratified between two others of a basic character." 

 He thus evidently considers that it comes from the same source 

 and has the same origin as the other rocks of the Lyttelton 

 system. After a careful examination of the rock itself and 

 the surrounding lavas, the writer has been forced to form an 

 opinion directly opposed to the expressed and written ideas of 

 the professor. 



As it would be impossible to give an intelligible description 

 without the aid of a diagram, part of an official chart of the 

 harbour and an enlarged rough sketch-map of the area ex- 

 amined are added (PI. XLIV.). In the chart it will be found 

 at the point A. The chart has a scale of If in. to the mile. 

 The sketch-map is intended to show only that part of the 

 district that has been actually examined, 



About half a mile from Lyttelton the Lyttelton-Sumner 

 Eoad passes an abrupt wall of a whitish rock, K, about 30ft. 

 high, extending about 70 yards up the face of the hill and 

 a few yards below the road, the wall being nearly at right- 

 angles to the direction of the road. As it is followed up the 

 hill this wall gradually decreases in height, and is ultimately 

 on a level with the surrounding ground. Higher than this 

 the outcrop cannot be traced at this point, but it turns sharply 

 to the right, and runs for some distance parallel with the 

 road. The highest point of this outcrop is about 490ft. above 

 sea-level. Between this height and 690ft. the slopes are 

 thickly covered with grass, except in one or two places where 

 basic lava that apparently overlies the trachyte crojDs out. At 

 a level of 690ft. above sea-level there is another wall-like 

 outcrop, which runs almost parallel to the direction of the road, 

 and is fairly constant in elevation. To the right it gradually 

 gets smaller, and disappears at C. On the left it ends some- 

 what abruptly at D. From this point to the top of the hill, 

 770ft., all the rock seems to be trachyte of the same character 

 as the first outcrop, audits resemblance is borne out on micro- 

 scopical examination. At E, along the crest of the hill, the 

 trachyte seems to disappear, and a little further on a wall-like 

 buttress of basic rock stretches across at right-angles to the 

 axis of the hill. Descending the hill from E to F, the ground 

 is strewn with boulders of the same rock; and at F, on the 



