Chemical Examination of Waters. 



147 



markable for purity. The total dissolved matter expressed in 

 grains per gallon, ranges from 3 64 (Wheeny) to 64 (Cataract). 

 The matter volatile at a low red heat, varies from 08 (Grose) to 

 2 - (Cataract). The fixed salts vary from 1*9 (Couridjah) to 4 - 9 

 (Woronora), The chlorine from 0'49 (Cox) to 303 (Woronora) ; 

 and the hardness from a mere trace (Couridjah) to 1'9 (Nepean, 

 at Douglass Park.) 



The following are the chief rivers examined flowing over sand- 

 stone, with their drainage areas : — 



Square miles. 



"Woronora 





48 



George's Eiver to junction of Toggerai 





70 



Cateract ... 





70 



Cordeaux... 



I 



284 



Upper Nepean ... 



Cox 





? 



Grose 





263 



Colo 





1575 



The first four drain the country lying near the coast to the 

 south of Sydney, the last four are more inland. It may be 

 noticed by reference to the table that the coastwise rivers contain 

 more chlorine (belonging chiefly to common salt) than the inland 

 rivers. This is, doubtless, owing to the fact that rain falling near 

 the sea contains a notable proportion of common salt. At the 

 University, Dr. Thomson has at various times carefully collected 

 rain apart from buildings, and has found the amount of chlorine 

 as follows : — 



Chlorine. 

 Date of Eain. 



7th December, 1867 



9th January, 1868 



2nd February, 1868 

 15th February, 1868 

 16th February, 1868 

 17th February, 1868 



The mean of these six experiments is 0413, corresponding to 

 0'68 of common salt. "We have had as yet no opportunity of ex- 

 amining rain water collected inland, but it is not to be expected 

 that it would yield chlorine to the same extent. 



The Eivers Cox, Grose, and Colo, in their upper portions, have 

 cut down through the Sydney sandstone and into the coal and 

 shales lying underneath, but these strata appear to furnish no 

 more soluble matter than the sandstone itself, for the three 



grs. per gal. 



Remarks. 



... 0-158 



Thunderstorm from 





westward. 



... 0-382 





... 0164 





... 0819 



Heavy gale" from S. 



... 0464 



Gale veering to E. 



... 0492 



E. gale abating. 



