216 ANNUAL OF SCIENTIFIC DISCOVERY. 



no signs of lead could be detected. This remarkable action Mr. Noad 

 ascribes to the presence of an unusually large quantity of organic 

 matter contained in the water. 



Dr. Nevins, of Liverpool, in a recent publication, shows, from inves- 

 tigations, that, whilst hard waters of a certain kind exercise a protect- 

 ing influence on lead, there are others which act energetically upon 

 this metal. The conclusions at which he has arrived, from numerous 

 experiments, are as follows : Hard waters do not protect lead, simply 

 from the fact of their being hard ; but this protection, when effected, 

 is dependent, not only upon the nature of the salt causing the hard- 

 ness, but also upon the proportion present ; for, whilst all experi- 

 ence proves that a small amount of sulphate, at any rate of sulphate 

 of lime, does protect the lead, a large quantity of sulphate of magnesia 

 acted considerably upon it. It appears to be proved, also, that chlo- 

 rides act upon lead, either with or without the presence of a sulphate ; 

 but their action is not so great as that of soluble carbonates. These 

 results do not practically affect the question of the safety of using lead 

 for common waters, so far as sulphates are concerned, as the experi- 

 ence of years proves that no bad consequences result from the employ- 

 ment of lead for water containing sulphates. 



ON THE ALTERATION WHICH WELL-WATER UNDERGOES. 



THE following results have been arrived at by M. Blondeau, from the 

 examination of the water of a great number of wells : 



1. Well-water may be altered by two causes : by the presence of 

 mineral salts held in solution, and by that of animal matters. 2. The 

 mineral substances which occur in solution are, silica, alumina, car- 

 bonates and phosphates of lime and magnesia, potash, alum, chlorides 

 of calcium, magnesium and sodium, with nitrates of the same bases. 

 These different substances are not hurtful to the animal economy when 

 they exist only in small quantity. Well-water, of which a litre con- 

 tains only four to five centigrammes of these substances in solution, 

 may be employed for all domestic uses, provided it does not contain too 

 large a proportion of animal matter. 3. Water, of which a litre con- 

 tains one gramme of the above-mentioned substances, may still be good 

 for drinking, but it is not fit for cooking vegetables, or washing linen, 

 when it contains 0.1 gramme of lime or magnesia. 4. Water, of 

 which a litre contains 0.1 gramme of lime or of magnesia, and 0.1 

 gramme of organic matter, is improper for any domestic use. 5. It is 

 of the utmost importance to state the existence and determine the 

 quantity of animal matter held in solution in waters ; for, if they exceed 

 the limits above stated, they act disastrously on the economy, and may 

 occasion dysentery and various maladies which appear to be contagious, 

 because the whole population acquire the seeds at the same sources. 

 6. The presence of magnesia in drinkable waters does not produce so 

 hurtful an action as supposed by some persons. Waters containing 

 on an average five times as much magnesia as the waters of the valley 

 of the Iser, in Switzerland, are used in many places, and yet endemic dis- 

 eases, as goitre and cretinism, are not known to exist in the same local- 



