32G . BOARD OF AGRICULTURE. 



rapidly on lead. Some of these agents coat the pipe with 

 compounds insoluble m water, which may be worn away by 

 the friction of the current, and slowly poison by its cumula- 

 tive action those who may drink the water. People are not 

 susceptible alike to the influence of lead. So small a quan- 

 tity as the hundredth of a grain to a gallon has been known 

 to cause paralysis, showing the subtle and dangerous char- 

 acter of the poison. 



Lead can be used for short service-pipes with comparative 

 safet3% if the water is allowed to run freely before using, and 

 for shallow wells, if the pump is vigorously used to wash out 

 the water that has stood for a time in the pipe. It is better, 

 however, to dispense with its use entirely, and substitute 

 iron, which is never harmful, and only objectionable on 

 account of its tendency to oxidation, which may be overcome 

 for a long time by dipping the pipes, while hot, in a bath of 

 coal-tar and coal-rosin. 



It has been proposed to coat the interior of lead pipe with 

 block tin, a soft metal. Experience has not proved its prac- 

 tical utilit3^ 



The use of earthen, glazed stone-ware pipe for aqueducts, 

 laid with cement joints, is an excellent method to preserve 

 the purity of the water. It is clean, durable, and, in many 

 localities, as good as iron. 



Water may be purified, when necessary, by distillation, 

 boiling, aeration, filtration, and by the addition of chemical 

 agents that are harmless, like alum, lime-water, charcoal, 

 and weak vegetable infusions that hold tannin in solu- 

 tion. 



Boiling expels the air, carbonic acid, carbonate of lime, a 

 part of the iron, and acids, and kills the microscopic infusoria, 

 bacteria, vibrios, and plant-life, that abound in most natu- 

 ral waters. Household purification is best effected by the 

 simplest methods, such as boiling, and filtration through 

 sponge, cotton-flannel, and tap-filters filled with quartz-sand 

 and animal charcoal. 



There are many devices invented that are excellent filters ; 

 but the best method is to secure water that needs no purifica- 

 tion, if possible. 



Water in the form of ice is both a luxury and a necessity 

 with most families, — a luxury in the hot months by cooling 



