OBSERVATIONS ON THE CORROSION OF STEEL IN WATER. 71 



They find that many salts at a certain concentration in the 

 solution show a maximum of corrosive power, but that on 

 further increasing the concentration, the corrosive power 

 rapidly decreases. We believe that the accelerative effect 

 of salts on corrosion is explained by the greater conducting 

 power of the solution. The decrease in the velocity of 

 rusting with higher concentrations of dissolved salt is 

 probably due to the decreased solubility of oxygen in the 

 solution. The experiments described in paragraph (6) were 

 conducted primarily with the object of testing the action 

 of some Artesian bore waters on steel. It has been sup- 

 posed for some time that the bore- waters in the Ooonamble 

 district are extra corrosive on steel or iron casings, and we 

 have tested two of these in our experiments. 



(5) Analysis Records of Bore Waters.— We have care- 

 fully examined the analyses of all the bore waters in the 

 State of New South Wales, with the object of seeing whether 

 any great variations are noticeable, which could account 

 for any special corrosion. The analyses records are con- 

 tained in a printed report kindly sent to us by Mr. L. A. B. 

 Wade, Department of Public Works of N.S.W. We have 

 noticed one characteristic which clearly marks off the 

 Coonamble district as being different from the others, 

 though we do not believe that this characteristic in itself 

 is a direct cause of special corrosion. 



There are approximately 440 bores (working) in New 

 South Wales; 100 of these are situated in the Ooonamble 

 district ; of these 51 show the presence of sulphates. 

 There are only 18 bore-waters in other parts of the State 

 which show the presence of sulphates. It is further notice- 

 able that as a bore is deepened, carbonates and chlorides 

 usually decrease in quantity, while there is a tendency for 

 increasing quantities of sulphate to be present. The sul- 

 phates are found in Ooonamble district at smaller depths 



