130 
IOWA ACADEMY OF SCIENCE 
A considerable number of the samples of water contain gas pro- 
ducing organisms, but in no instance did we find the colon bacillus, 
excepting in the water from the Taylor Creek camps. The small 
number of organisms in the water from various sources, excepting 
the logging camps, when plated soon after collecting, indicates a 
good supply of water and little organic matter. The temperature 
of the water at different points is such that organisms do not multi- 
ply rapidly. The temperature of the water at different points is 
indicated in the following table : 
Locality 
Time 
Tempera- 
ture of 
water 
Tempera- 
ture of 
air 
Swamp south end of lake, surface 
4:30 P. M. 
69 
1 foot from surface 
4:30 P. M. 
68 
Cedar Lake, water near shore 
4:30 P. M. 
69 
Power House, Cedar River 
7:00 P. M. 
66 
Mouth Cedar River, head of lake .• 
3:00 P. M. 
70 
Swamp, Cedar River, upper end of lake 
3:30 P. M. 
69 
Cedar River dam 
1:30 P. M. 
68 
72' 
Cedar Lake, i mile from dam 
1:40 P. M. 
69 
72 
Cedar Lake, 1 mile from dam 
2:00 P. M. 
68 
72 
Cedar Lake, 2 miles from dam 
} 2:30 P. M. 
68 
72 
Cedar Lake, southwest shore rocky promontory 
! 3:00 P. M. 
70 
72 
Cedar River, half way to power house 
10:00 A.M. 
61 
66 
Cedar River water, 2£ miles from power house to Barnes- 
ton 
8:00 P. M. 
64 
Taylor Creek, 1 mile from Barneston 
9:00 A.M. 
50 
68 
Taylor Creek, £ mile up stream 
10:00 A. M. 
55 
80 
Taylor Creek 
11:30 A. M. 
42 
84 
Spring Water 
11:45 A. M. 
43 
84 
There seems to have been a difference of opinion with reference 
to the nature of the soil as a filter medium. The writer, in his re- 
port on this subject, made the following statement: 
The water dropping on the humus, percolates through the humus 
and a carpet of many small plants and humble mosses, then into a 
stratum of sand and gravel mixed in such way as to make a good 
filter. 
Professors Sedgwick, Harrington, and Abbott quoted elsewhere 
in this paper, made a statement that it was not an ideal filter. It is 
true as I have said, that at two points there are beds of clay, but 
nowhere along the proposed right of way. To test the efficiency 
of filtration, samples of soil were collected at different points and 
on my return home the soil was placed in galvanized iron cylinders 
18 inches long. Ordinary deep well water having an average of 40 
bacteria per cc. was allowed to percolate through the soil and the 
