TYPHOID FEVER IN DISTRICT OF COLUMBIA. 
29 
The following bacteriological results upon the colon bacillus 
obtained in the laboratory of the filtration plant are given for com- 
parison : 
July 16 to Oct. 16. 
Quantity. 
Number 
positive. 
Per cent 
positive. 
Dalecarlia inlet 
cc. 
10.0 
10 
19 
1.0 
9 
17 
.1 
17 
33 
Dalecarlia outlet 
10.0 
13 
25 
• 
1.0 
11 
21 
.1 
11 
21 
Georgetown 
10.0 
11 
21 
1.0 
12 
23 
.1 
8 
16 
Washington City reservoir 
10.0 
14 
19 
1.0 
13 
17 
.1 
•0 
0 
Filtered water reservoir 
10.0 
3 
4 
1.0 
1 
1 
Tap water 
10.0 
6 
6 
1.0 
5 
4 
CHEMICAL ANALYSES OF THE POTOMAC WATER SUPPLY. 
The following are the results of the chemical analyses of the water 
of the several reservoirs and storage basin for the period covered by 
our investigation, viz, from July 30 to September 27, 1906, together 
with a table showing the improvement in parts per million and in per 
cent of the water of the Potomac River accomplished by subsidence 
and filtration: 
Averages of 14 analyses of the waters of the reservoirs and storage basin, made at intervals 
of 3-4 days to 1 week from July 30 to September 21 , 1906. 
Name of reservoir. 
Turbid- 
ity .a 
Total solids. 
Chlo- 
rine. 
Ammonia. 
Total 
residue. 
Mineral 
matter. 
V olatile 
matter. 
Free. 
Albumi- 
noid. 
Dalecarlia inlet 
221.0 
203 
156 
47.1 
2.6 
0.024 
0.161 
Dalecarlia outlet 
99.0 
163 
115 
4&0 
2.61 
.027 
.131 
Georgetown 
55.2 
160 
111 
49.0 
2.61 
.022 
.117 
Washington City (unfiltered) 
46.3 
141 
100 
41.0 
2.47 
.017 
.096 
Storage basin (filtered) 
4.6 
127 
88 
39.0 
2.53 
.015 
.054 
a Average of all readings made. 
