131 



This deposit, which adheres firmly to the lead, does not fall uniformly 

 over the surface of the metal, but in spots or lines over the bottom and 

 along the edges of the solder within the cistern, and upon analysis 

 proves to be carbonate as weU as sulphate of lead, and also contains 

 oxide of tin. It is, therefore, obviously the result of a galvanic action 

 between the lead and the solder, which goes on to the complete cor- 

 rosion of the lead, and is sustained with greater energy in proportion 

 as the water is harder, or contains more chloride. Many interesting 

 pieces of lead from old cisterns were exhibited, illustrating the nature 

 of this action. 



In reference to the Rivington water, the authors had instituted a 

 large series of experiments, upwards of sixty in number, and extending 

 over a period of six weeks, with a view of fully investigating its action 

 upon lead. The water was taken by themselves from the reservoirs of 

 Anglezark, Eivington, and Prescot, and from the wells at Green-lane. 

 In every case the Rivington water acted distinctly, and in some 

 cases, largely on the lead. In no case was any dissolved by the 

 well water from Green-lane. 



A general analysis of the water taken from the head of the Riving- 

 ton reservoir, gave Dr. Edwards the following result : — 



Gr. ^ Imp. 

 Gallon. 



Carbonate of Lime and Magnesia 1-01 



Silica 0-20 



Oxide of Iron (trace). 



Sulphate of Lime 2-30 



Chloride of Sodium 1-90 



Organic Matter 2-06 



Free Cai-bonic Acid, IJ cubic inch. 



7-47 

 It would appear, as the result of these experiments, that the quantity 

 of sulphate and carbonate of lime is too small to afford the necessary 

 amount of protection. Comparative experiments were made with 

 scraped lead, dull cistern lead, old cistern lead, new and old pipe lead, 

 &c. Two new cisterns were also prepared, each holding about a 

 gallon, from which at various periods samples of the water were drawn 

 off and analysed. In twenty-four hours the presence of lead was 

 apparent, and increasingly so up to thirty-three days, when the whole 

 was evaporated, the lead precipitated, and found to amount to about 

 three grains of lead per imperial gallon. The cistern being again 

 charged, and left eleven days, yielded, upon evaporation, nearly two 

 grains of metallic lead for each imperial gallon. 



The cistern was again filled, and examined at the end of seven 



