ROCK TEMPERATURES AT SYDNEY HARBOUR COLLIERY. 209 



to the 1,150 feet level they were put in a distance of 4 feet in 

 each case. Beginning at the 1,150 feet level the two maximum 

 thermometers were used, in addition to the two slow-action instru- 

 ments, 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. 



After the completion of the drilling, the holes were allowed to 

 remain open for a period of from 34 to 84 hours (as specified in 

 the table appended) in order that the heat generated by drilling 

 might escape before the thermometers were inserted. The 

 thermometers were then taken down the shaft and read immedi- 

 ately before being placed in position in the holes. This was done 

 in the case of the maximum thermometers, to ascertain that they 

 then registered a lower temperature than that likely to be observed 

 on their withdrawal from the holes, and in order to ensure this, 

 the instruments were, excepting during the winter, steeped for 

 some time in cold water before being placed in the holes. To the 

 copper cases enclosing the thermometers, strong pieces of string 

 were attached to facilitate their subsequent withdrawal from the 

 holes, and when the instruments were in position 'end on' to one 

 another at the back of the holes, the strings extended from the 

 cases to a little beyond the mouths of the holes. The plugging of 

 the holes consisted, in each case, of about six inches of greasy 

 cotton waste, placed next to the thermometers and gently rammed 

 against the outer instrument case with a wooden rammer, the 

 remainder of the hole being filled up with plastic clay, rammed 

 into the hole. Attached to the cotton waste, in each hole, was a 

 piece of pliable wire, by means of which the plugging could be 

 quickly withdrawn after the clay tamping was removed by a 

 scraper. 



After being left in the holes for a period of from 37 hours 

 upwards (as specified in the table appended) the clay tamping 

 and cotton waste plugging were removed from the holes, and the 

 thermometers pulled out by means of the strings and read immedi- 

 ately. In the case of the slow-action thermometers the thick 



N— Dec. 6, 1899. 



