560 Transactions. 



of the tank rendered the solution in good condition for the 

 extractor-boxes. 



By this method of treatment the following results were 

 obtained : (a) The reaction in the extractors was rendered 

 normal ; (b) the bullion - extractions were all that could be 

 desired ; (c) the cyanide - consumption was reduced from 4s. 

 to Is. 6d. per ton ; (d) the zinc -consumption was reduced to 

 about one- quarter ; besides, there was a much less quantity 

 of slimes to handle. 



Art. LXIII. — Geological Notes on the Country North-west of 



Lake Wakatipu. 



By Dr. P. Marshall. 



[Read before the Otago Institute, \4th November, 1905.] 

 The country to the west of Lake Wakatipu has been but seldom 

 visited. It has, however, been twice reported on in a general 

 way by geological observers. 



Professor Park in 1887 made a flying reconnaisance through 

 the district, and gave a general description of the geological for- 

 mations he met with in the Reports of the Geological Survey. 

 Professor Ulrich in 1890 published in the " Quarterly Journal of 

 the Geological Society " a general account of the rocks of the 

 district, compiled from examination of specimens collected by 

 several explorers. 



An expedition was made in January, 1905, by myself, with a 

 party of students from the Otago University School of Mines, and 

 Mr. A. E. Flower, of Christ's College. As the district is still 

 without any tracks, and is traversed by mountain-ranges of an 

 extremely precipitous nature, while the valleys support a dense 

 growth of forest, it was recognised that difficulties greater than 

 those that usually impede a geologist would have to be encoun- 

 tered. Fifteen days' provisions were taken, as well as an ordi- 

 nary camping-outfit, so each man had to carry a load of 45 lb. 

 at the start. The object was to cross over to the west coast 

 via the Rock Burn, Hidden Falls, Olivine, and Pyke Streams, 

 and to ascend the Red Hill Mountain of olivine formation. 

 The weather experienced entirely prevented this result, and the 

 expedition was unable to proceed much further than the head 

 of the Olivine Stream. Geological and physiographical observa- 

 tions were made on the way, in the hope that some additional 

 information might be gleaned as to the origin and nature of the 

 surface features and structure of this out-of-the-way part of the 

 country. 



