ROCK TEMPERATURES AT SYDNEY HARBOUR COLLIERY. 



221 



The water flowing into the shaft from between the "water rings" 

 fixed at the 442 feet and 768 feet levels, is remarkably rich in lime, 

 with distinct traces of barytes. So much lime is present that, in 

 the space of a fortnight, the two inch pipe, leading the water 

 down from the 768 feet level to the bottom of the shaft, became 

 almost completely blocked with a solid fibrous, radial incrustation 

 of barytic carbonate of lime. The iron pipes were consequently 

 replaced with wooden boxes, three inches square, which can be 

 taken to pieces when it is necessary to remove the incrustation. 

 As the two inch wrought iron pipes from the " water ring " at the 

 442 feet level show no signs of lime incrustation, it is evident that 

 it comes from somewhere between the 442 feet and 768 feet levels. 

 Mr. H. G. Smith, f.c.s., and one of us (Professor David) have 

 already noticed the occurrence of barytes in the Hawkesbury 

 series, but this abundance of lime in the Hawkesbury Sandstone 

 is quite exceptional. 



IV. Diagram showing Temperature Curve and Table of Records 

 of Rock Temperatures. — The following curve diagram and table 

 give full particulars of the results of the observations made in 

 the Birthday Shaft :— 





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