138 FIRESIDE SCIENCE. 



pyrites, or sulphuret of iron. This mineral is usu- 

 ally found in the form of little cubes, very hard and 

 dense, and having a golden yellow color. These 

 cubes are often supposed by well-diggers to be true 

 gold. We receive a carefully done-up package 

 of this mineral as often as once a week during the 

 year, sent to us for chemical analysis, the finder be- 

 lieving he has discovered a gold mine. We are 

 always sorry to be compelled to furnish results 

 which demolish the foundation upon which rest 

 " great expectations." Waters brought in contact 

 with such minerals are often impregnated with an 

 offensive gas (sulphuretted hydrogen, or sulphydric 

 acid) and the taste is unpleasant. Their action 

 upon leaden pipes is of an unfavorable nature, pro- 

 ducing sometimes rapid decomposition. We have 

 not sufficiently investigated the nature of this action 

 to be able accurately to define it ; but it is certain 

 it occurs, and leaden pipes should not be employed 

 to conduct such waters. Organic matter from 

 vaults and cesspools frequently finds its way into 

 wells, and changes the character of waters, so that 

 they become dangerous in their influence upon lead. 

 Some waters are decidedly alkaline, and thus the 

 action of carbonic acid upon lead oxide is neutral- 

 ized, and it remains in solution. 



The nature of the action of water upon lead is 

 changed from local causes, operating within the 



