383 



Sarsen Stones and Drift Pumice in New Zealand. 



Extracts from a letter from Mr. R. Speight, M.A., 

 M.Sc.: — 



"There are many points of more than ordinary interest 

 to me in your 'Geological Memoranda.' We have here in 

 Otago numerous 'sarsen' stones, called by the miners 'china- 

 men,' which lie on the surface of the schist area. Sections 

 made from them show that they are formed by the cementation 

 by silica of quartz grains and pebbles derived from what is 

 called the quartz-drift, a loose conglomerate of quartz pebbles, 

 etc., which contains the alluvial gold of the old basin of Otaeo. 

 The great majority of this has been stripped off by erosion, 

 leaving the 'chinamen' on the surface. Miners nearly always 

 regard them as favourable for gold, as this is occasionally 

 found under them," 



"Your note on 'Pumice Drift' is also interesting. One 

 can hardly explain the presence of pumice in drift material 

 on this coast on the present distribution of ocean currents. 

 Although pumice is plentiful in the North Island, it is found 

 on the shores in all parts of the South Island, and specially 

 of Stewart Island. This may be carried down the west coast 

 and lodge at Stewart Island by a branch of the Australian 

 current, but the shore drift is generally from south to north. 

 Much of the flotsam of the Tasman fetches up on Stewart 

 Island." 



Walter How chin. 



Evening Meeting, May 13, 1920. 



Notes on X=Ray Phenomena. 



1. Phenomena in a Punctured "Coolidge" X-ray Tube. 



The exhibited tube is one having done three years of very 

 heavy service in the X-ray Department at Keswick. It 

 recently failed owing to puncture. Upon admission of air, 

 the incandescent filament of the cathode evidently combined 

 with oxygen with the formation of an oxide of tungsten, which 

 is shown by the dense white deposit. The purple manganese 

 colouration of the glass, due to bombardment by X-rays, is 

 now very beautifully shown, owing to the white background 

 of the oxide of tungsten. Certain beautifully rich sections 

 suggest industrial applications in Ceramics. Several bands of 

 differential deposit of the oxide well illustrate the physics of 

 the tube existent at the time of puncturing. 



A. R. Riddle. 



Evening Meeting, November 13, 1919. 



M 



