and the Constituents of Well- and Rwer-waters. 205 
Here we have an instance of a water containing a large quan- 
tity of the so-called preservative salts acting strongly upon lead. 
It may be remarked, that, in making the analysis of this water, 
the author sought neither for nitric acid, ammonia, nor any 
other oxidation product of nitrogenous organic matter, although 
we may assume them to have been undoubtedly present. To 
what, the author inquires, are we to ascribe this remarkable 
action on lead? The reply is, “ to the large quantity of organic 
matter.” It was noticed that the corrosion of the lead occurred 
chiefly in the summer months, at a time when the decomposition 
of organic matter is assumed to be most active. The author 
explains the absence of lead in the clear water, on the assump- 
tion that the carbonic acid arising on the bottom and sides 
of the cistern from the decomposition of organic matter, com- 
bines with the oxide of lead floating on the surface of the water, 
and forms the carbonate which, unlike the carbonates of lime 
and magnesia, is almost absolutely insoluble in excess of car- 
bonic acid. Other examples are quoted of water containing 
large quantities of sulphates and chlorides (which are supposed 
to have a protecting influence) acting strongly on lead; and in 
every instance, except in the case of the Highgate water, the 
water contained very large quantities of organic matter. Finally, 
the author found the deep well-waters of the London basin to 
act upon lead; and he attributes, in this case, the solvent action 
to be due to the alkalinity of the waters. Here we find, in the 
papers quoted, the action of water on lead attributed,—l1st, to 
the presence of nitrates; 2ndly, to organic matter; 3rdly, to the 
presence of free alkali. Numerous other authors, amongst them 
Guyton Morveau, Christison, Captain Yorke, Dr. Lambe, &c., 
might be quoted; but as the investigations of these authors tend 
to throw but little light on the subject, I shall, before entering 
into details of my own experiments, allude only to the opinions 
of the Government reporters, Professors Graham, Hofmann and 
Miller, who, at the request of Government, paid particular atten- 
tion to the action of waters upon lead*. 
In reply tothe question, ‘‘ Whether any comparative inconve- 
nience would arise from a supply of soft water to the metropolis,” 
the authors remark upon the solvent action of soft waters upon 
lead as being calculated to excite alarm. It does not appear, 
however, that the soft waters from the Surrey Hills, which con- 
tain, on the average, only 6 grains of solid matter in a gallon 
and have a hardness of only 2 degrees, have any appreciable 
action on lead, with the exception of that from the Punch-bowl, 
of which the power of acting on lead seemed to be very consider- 
able. Even river- and spring-water from the chalk strata, arti- 
* Quart. Journ. Chem. Soe. vol. iv. p. 400. 
