118 



FARM APPLIANCES. 



deep ; or a round o'ne, fifteen feet in diameter, would need 

 to be about twelve feet deep. In the far West in fact, 

 in most places west of the Missouri the rainfall is 

 largely during the six months beginning with March, 

 and cisterns need a greater storage capacity. 



CISTERNS WITH FILTERS. 



Complaints are frequent of the impure water of cis- 

 terns. This is inevitable under the careless manage- 

 ment of these useful additions to the water supply, and 

 is a fruitful source of what are called " malarial dis- 



Fig. 143. A COMPLETE CISTEBN. 



eases." A roof gathers a large quantity of impure mat- 

 ter, dead insects, droppings of birds, dust, dead leaves, 

 pollen from trees, etc., etc., all of which are washed into 

 the cistern, unless some means are taken to prevent it. 

 Even then the water should be filtered before it is used 

 for culinary purposes. One way of preventing foul mat- 

 ter from entering the cistern, is to have the leader mov- 



