Park. — The Bock-phosphates of Otago. 391 



watershed of the streams flowing into the lake, or the ice 

 forming the glacier scooped them up from the bed of the lake. 

 So far as our stratigraphical knowledge of the district goes, the 

 latter explanation is possible, for the crystalline schists at the 

 Hollyford underlie the Te Anau series. This latter series also 

 borders the west side of the upper portion of the lake, and, as 

 the lake has a depth of 1,200 ft., it is possible that tbe under- 

 lying rocks may be exposed in the bed. of the lake. Several 

 instances are on record of rocks having been raised by ice- 

 action from low to high levels. 



The presence of the porphyrite strongly supports Captain 

 Hutton's theory that a glacier from the Shotover acted as a 

 tributary to the Lake Wakatipu glacier. 



Whether these rocks now occur in the drainage-basin of 

 the lake or not, there is no doubt that the lake-bed must once 

 have been the bed of a large glacier which existed long enough 

 for rock-fragments to be borne some hundred miles on its 

 surface. A record of their occurrence may therefore be of 

 service hereafter, when sufficient facts have been collected to 

 enable us to solve for ourselves the question on its own merits 

 whether the rock-basin of Lake Wakatipu owes its origin to 

 glacial erosion or earth-movements. Earth-movements in the 

 mountains bordering the lake must almost certainly be re- 

 corded by the tilting of the terraces formed round the lake- 

 shores. No accurate measurements of the height of these 

 terraces in different portions has yet been made, though Mr. 

 McKay mentions such terraces at a height of 1,000 ft. near 

 Queenstown, and at 300ft. further up the lake. He does not, 

 however, say that his observations refer to different parts of 

 the same terrace. 



Art. XLVIII. — On the Geology of the Bock-phosphate De- 

 posits of Clarendon, Otago. 



By Professor James Park, F.G.S., Director, Otago Univer- 

 sity School of Mines. 

 [Read before the Otago Institute, 11th November, 1902.] 



The discovery of rock-phosphate was made some two years 

 ago by Mr. Ealph Ewing, of Whare Flat, Dunedin, who 

 qualified himself for the work of prospecting by a personal 

 study of the phosphate-deposits of the United States of 

 America. Mr. Ewing, on his return from America, made a 

 systematic search of the east coast districts of Canterbury 

 and Otago, and finally located the present deposits on what 



