204 Mr. H. Medlock on the Reciprocal Action of Metals 
Neither ammonia nor nitric acid appear to have been looked for 
in the water of the Don. 
A very able and important paper by Dr. Noad*, “On the Com- 
position of certain Well-waters in the neighbourhood of London, 
with some observations on their action upon Lead,” was published 
in 1852. The author was led to examine a sample of water from 
a well near the old church of Highgate, in consequence of the 
powerful action of the water on leaden pipes and cisterns, and 
also from the large amount of solid matter it contamed. Of 
organic matter there was no appreciable quantity, but the pro- 
portion of nitric acid resulting from the decomposition of animal 
remains was present in extraordinarily large quantities, as will 
be seen from the subjoined analysis :— 
Grains in a gallon. 
Siligg:; 2) OR, DO Dale me Jeune BREE 
Sulphate of potash. . . . . 17-0448 
Sulphate of soda . . . . . 95152 
Chloride of sodium. . . . . = 9°6820 
Chloride of calcium. . . . . 5°9120 
Nitrate of ime . . . . . . 4071200 
Nitrate of magnesia . . . . 17:0640 
100°1840 
From this analysis there appears to be the extraordinary 
quantity of 88:87 grains of actual anhydrous nitric acid in each 
gallon of the water ! 
Another sample of water from a spring at Clapham was ana- 
lysed by Dr. Noad in 1848. This water likewise acted strongly 
upon lead. A leaden cistern filled with this water was examimed 
at the same time, and the surface of the water was observed to 
be coated with a “thick, greasy scum, which proved on exami- 
nation to consist almost entirely of oxide of lead.” No signs of 
lead could be detected in the clear water beneath the scum. 
This water had the following composition :— 
Grains in @ gallon. 
ACR Sc es 
Carbonate of lime . . . . . 15°09 
Carbonate of magnesia. . . . 18°97 
Sulphate of lime;.. .. ... «. . 282 
Sulphate of potash. . . . . 679 
Sulphate: of fodais i. ton S svi. lOW7 
Chloride of sodium. . . . . 11°46 
Organie:matter oF 2926) .p079 410 
77°74 
* Quart. Journ. Chem. Soe. vol. iv. p. 20. 
