208 J. L. C. BAE, E. F. PITTMAN, AND T. W. E. DAVID. 



wrought iron pipe, hermetically sealed at both ends by means of 

 screw cap pieces which were screwed on hot, with molten lead in 

 the threads of the screws. The results of these observations have 

 been recorded by two of us elsewhere. 1 



The results of these observations show that the rate of increase 

 of rock temperature downwards at Oremorne is about 1° Fahr. for 

 every eighty feet. Shortly after these observations were made at 

 Cremorne, Professor Everett kindly sent another protected Negretti 

 and Zambra maximum thermometer, as well as a protected 

 Phillips maximum thermometer, for further observing of under- 

 ground rock temperatures. The thermometers used on the present 

 occasion were the two slow-action and the two maximum Negretti 

 and Zambra thermometers sent by Professor Everett. Their 

 numbers are 50452 and 50454 (slow-action) and 15888 and 65294 

 (maximum). 



II. Methods of Observing. — The observations of underground 

 temperatures at the Sydney Harbour Colliery, Balmain, Sydney, 

 were obtained by the methods recommended by the Underground 

 Temperature Committee of the British Association for the 

 Advancement of Science. The sinking of the Birthday Shaft had 

 reached a depth of 600 feet before the first observations were 

 made, but since then, readings of the rock temperatures have been 

 taken at intervals of practically 50 feet, and an opportunity will 

 be afforded of making observations at less depth than 600 feet 

 during the sinking of the Jubilee Shaft, which is situated at a 

 distance of 168 feet from the Birthday Shaft (the distance given 

 being from centre to centre of shafts) and has reached, at the 

 present time, a depth of 225 feet. 



From 600 feet down to 1,100 feet only the two slow-action 

 thermometers were used, and the horizontal holes, which were 

 drilled into the walls of the shaft for their reception, were put 

 in a distance of 3 feet down to the 950 feet level, while from that 



l T. W. E. David and E. F. Pittman— Records Geol. Survey N. S. W., 

 1894, iv., pt. 1, p. 7; Proc. Roy. Sec. N.S.Wales, 1893, xxvn , pp. 

 460 - 465. 



