700 Proceedings of the Royal Society 
The general results of the former inquiries are — 1 That the 
purest waters act the most powerfully on lead, corroding it, and 
forming a carbonate of peculiar and uniform composition ; 2. That 
all salts impede this action, and many prevent it altogether, some 
of them in extremely minute proportion ; and 3. That the proportion 
of each salt required to prevent action is nearly in the inverse ratio 
of the insolubility of the compound which its acid forms with the 
oxide of lead. The effect of certain inorganic and organic ingre- 
dients of water in modifying the preservative power of the salts 
was not investigated, but has been since made the subject of nume- 
rous observations and inquiries by others, chiefly, however, of a 
desultory nature, some of them much too succinctly described, and 
some also of questionable accuracy. 
The first part of the present paper dealt with the influence of 
inorganic substances. The second part, on the influence of organic 
matters, was reserved for a subsequent article. 
It had been denied thatwater acts by reason, and in the ratio, 
of its purity; and it had even been alleged that distilled water 
itself does not act, if really quite pure. The author, however, had 
invariably found the reverse, and could assign no other explanation of 
these statements except some error in manipulation. For example, 
a very pure spring water was sent to him from the south of England, 
with the assurance that it had been found to be incapable of attach- 
ing lead. But, on making trial of it, he had found it act with an 
energy not inferior to that of distilled water. Also, it had been 
stated that ordinary distilled water is apt to contain a trace of 
nitric or nitrous acid, from nitrates incidentally present in the 
water subjected to distillation ; and that such water, it distilled 
after the addition of a little potash to fix the acid thoroughly, 
yields a distillate which has no action on lead. But when the 
author prepared distilled water in this way, with great care to 
prevent the access of impurities from other sources, the only 
result was that the action was even greater than that of the 
ordinary distilled water of the laboratory, and so great as he had 
never observed before. 
An interesting statement had been made by Dr Nevins, that 
some salts appear to allow of a certain action going on when they 
are present largely in water, although their influence, when they 
