30 
TYPHOID FEVER IX DISTRICT OF COLUMBIA. 
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 27, 1906 — Continued. 
Name of reservoir. 
Nitrites. 
Nitrates. 
Dissolved 
oxygen. 
Per cent 
of satu- 
ration. 
Oxygen 
consumed. 
Dalecarlia inlet 
0.0031 
0.61 
7.44 
89.6 
4.1 
Dalecarha outlet 
.0051 
.57 
7.62 
92.4 
3.4 
Georgetown 
.0065 
.60 
7.44 
90.0 
3.3 
Washington City (unfiltered) 
.0056 
.61 
7.60 
90.0 
3.0 
Storage basin (filtered) 
.0003 
.67 
5.87 
71.4 
2.0 
Chemical improvement of Potomac water as the result of subsidence and filtration. 
[Compiled from analyses made in the division of chemistry of the Hygienic Laboratory, covering a period 
of 11 weeks, from July 16 to September 28, 1906.] 
Turbid- 
ity. 
Total solids. 
Chlo- 
rine. 
Ammonia. 
Total 
residue. 
Mineral 
matter. 
V olatile 
matter. 
Free. 
Albumi- 
noid. 
Dalecarha inlet 
221.0 
203.0 
156. 0 
47.1 
2.6 
0.024 
0.161 
Storage basin 
4.6 
127.0 
88.0 
39.0 
2.53 
.015 
.054 
Improvement in parts per million . . 
216.4 
76.0 
68.0 
8.1 
^ .07 
.009 
.107 
Improvement in per cent 
97.9 
37.4 
43. 5 
17. 1 
2.7 
37.5 
• 66.0 
Nitrites. 
Dissolved 
oxygen. 
Per cent 
of satu- 
ration. 
Oxygen 
consumed. 
Dalecarha inlet, 
Storage basin 
Improvement in parts per million 
0.0031 
.0003 
.0028 
90.0 
7.44 
5.87 
89.6 
71.4 
4.1 
2.0 
2.1 
51.0 
Improvement in per cent 
Dissolved oxygen consumed in oxidation, 21 per cent. 
THE RELATION OF THE POTOMAC RIVER WATER TO TYPHOID 
FEVER. 
The t}^hoid fever bacillus has never been isolated from the Poto- 
mac River water. We therefore have no direct evidence to prove or 
disprove that some of the infection may or may not be water borne. 
We must, then, satisfy ourselves for the present with certain indirect 
evidence bearing upon this important question. 
Despite the improvement in the water, due to storage, sedimenta- 
tion, and filtration, no appreciable change in the typhoid situation is 
apparent. 
Water-borne epidemics, due to concentrated and quickly trans- 
ferred infection, may occur at any time of the year, particularly in the 
spring and late fall. Such epidemics are generally characterized by 
sudden onset and sharp decline. Little is known of the characteristics 
of typhoid-fever outbreaks resulting from water containing greatly 
diluted and slowly transferred infection. 
