My attention has for several years been directed to the state of the water with which the metropolis is supplied; and upon having been lately requested to propose a remedy for preventing the action of a spring in the neighbourhood of London upon lead, which it had been found to corrode in a very rapid manner, I suggested the expediency of protecting the pipes and cisterns with surfaces of iron; but before such a plan was put in execution, I proposed to try its efficacy in the laboratory:--the first result was very startling; for, instead of preventing, as I had anticipated, I found that it greatly increased, the solution of the lead. After various experiments, I arrived at the conclusion, that lead, when rendered negative by iron, and placed in contact with weak saline solutions,--such, for instance, as common spring water,--was dissolved; in consequence of the decomposition of the salts and the transference of their elements according to the general law, the acid passing to the iron, and the alkali to the lead; and so powerfully is this latter body acted upon by an alkali, that, if a slip of it be immersed in a solution of potash or soda, its crystalline texture is so rapidly developed, that its surface exhibits an appearance similar to that presented by tin-plate, and which is designated by the term _moirée_. I apprehend that most of the anomalous cases of the solution of lead in common water, which have for so many years embarrassed the chemist, may thus receive an explanation. An eminent physician lately informed me, that some time since he was called upon to attend a family who had evidently suffered from the effects of saturnine poison, and that he well remembers there was an iron pump in the cistern that supplied the water. Upon showing the results of my experiment to a no less eminent chemist, he was immediately reminded of a circumstance which occurred at Islington, where the water was found to corrode the lead in which it was received: in this vessel there was an iron bar; and the fact would not have attracted his notice, nor have been impressed upon his recollection, but from the unusual state of corrosion in which it appeared. I shall conclude these observations by an account of "the change which some musket balls, taken out of Shrapnell's shells, had undergone," by Mr. Faraday, and which is published in the 16th volume of the Quarterly Journal of Science, for the year 1823. This history is not only interesting on account of the high chemical character of its author, but satisfactory as being in direct opposition to previously established facts; and cannot therefore have received any bias from preconceived theory.