47 
FOR WAGGONER’S BIOLOGY 
II. Filtration. Prepare three filters as follows: 
No. 1. Place filter paper in a glass funnel. 
No. 2. Place fine sand three inches thick in a funnel. (Stop 
the opening with cotton.) 
No. 3. Place powdered bone charcoal in a funnel as in No. 2. 
Filter muddy water through each of these. Is there any differ¬ 
ence in the results? Which is the best method, judging from the 
filtered specimens? Add some coloring to the water or use colored 
cistern water, and repeat the filtering. Is the coloring removed in 
any case? 
III. Chemical Removal of Sediment. Add a little alum solu¬ 
tion to each of several samples of muddy pond or creek water. 
Allow to stand for some time. Note the results. Filter through 
filter paper. Again note the results. What is the use of the alum? 
IV. Does settling water free it from all impurities? Does it 
help? Why? Is this method used in your city water system? Is 
any one of the above filtration methods in use in this system? If 
so, how does it help? Is alum added to the water in your city? 
Will the settling, filtration, and addition of alum remove all danger 
from the use of the water? Explain. What else is needed in addi¬ 
tion to the removal of the sediment in the water? 
EXERCISE 50 
THE CITY WATER SUPPLY 
A class trip to the city water system may be made if the system 
is one which provides for the purification of water from a lake, a 
river, or other stream. 
I. The Reservoir. What is the source of the water which finds 
its wav into the reservoir? Is there evidence of the presence of any 
springs which may furnish a part of the water? Does the ap¬ 
pearance of the water undergo any change while in the reservoir? 
Does the change occur slowly or rapidly? Note living plants or 
