xlviii. ABSTRACT OF PROCEEDINGS. 



opportunity will be got of recording temperatures at less depth 

 than 600 feet, when the sinking of the Jubilee Shaft is gone on 

 with. From 600 feet down to 1,100 feet two slow action thermo- 

 meters 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 950 feet, and 4 feet from that to the 

 1,100 feet level. Beginning at the 1,150 feet level two maximum 

 thermometers were used, in addition to the slow-action instruments, 

 and the practice has been to place one instrument of each type in 

 each of the holes, which have been put in to a distance of 5 feet. 

 The plugging in each case consisted of about six inches of greasy 

 cotton waste, placed next to the thermometers, the remainder of 

 the hole being filled up with plastic clay rammed into the hole. 

 Every precaution was taken to ensure accuracy of results. If the 

 mean annual temperature of Sydney be taken as 63° Fahr., the 

 rate of increase is shown, by the observations made, to be at the 

 rate of 1° Fahr. for every 90Jfeet, which is fairly low, and may 

 be taken as a favourable indication for the future ventilation of 

 the mine. A remarkable increase of temperature was noted as 

 the sinking passed from the Hawkesbury Sandstones into the 

 Narrabeen Beds, the upper section of which consists of chocolate 

 shales. These shales, which outcrop on the sea coast at Narrabeen 

 some eight miles to the north of Manly, were struck in the shaft 

 at a depth of 1,024 feet 9 inches, or at practically the same depth 

 from the surface as in the Cremorne Bore, the exact difference 

 being 59 feet 7^ inches, measured from mean low-tide level in 

 Sydney harbour, the shaft being the deeper of the two. This is a 

 very slight difference in three and a quarter miles, which is the 

 distance from the shaft to the bore, the bearing being N. 67° 15'E. 

 A section of the strata, already passed through in the sinking of 

 the shaft, and a table, giving full particulars of the nature of the 

 rocks in which the temperatures were observed, time allowed for 

 heat generated by drilling to escape between completion of holes 

 and insertion of thermometer, time thermometers were left in the 

 holes, readings, corrections etc, were given along with the paper. 



