The Sanitary Engineer and the Public Health. 49 
and this it sometimes does in Houston. During the coldest spell of 
weather that we had last winter the daily paper stated that, owing to the 
excessive demand made upon the water supply, due to the fact that fau- 
cets were kept open to prevent freezing, the wells were unable to furnish 
sufficient water to keep up the required pressure, and bayou water was 
pumped directly into the mains, the color and odor for days afterwards 
bearing evidence to the fact. However, it is probable that Houston will 
remedy this condition in the comparatively near future, as surveys have 
been made and plans adopted for the purification of the city’s sewage, 
though some of the local engineers seem to doubt the effectiveness of the 
methods adopted because of local conditions. Indeed, I believe that 
work has been begun upon the construction of the trunk sewers that will 
be needed in collecting the sewage and bringing it to the pumping sta- 
tion. This very commendable determination on Houston’s part was 
brought about, not so much by the desire to improve the health condition 
of the city, as by the fact that some such sewage treatment was made a 
condition of the passing of a congressional appropriation for the improve- 
ment of Buffalo Bayou. People are quick to make expenditures when 
they see commercial gains in consequence, but strangely slow when it is 
only a matter of health — particularly if it happen to be some one else’s 
health that is in danger. 
How, since the conditions are fast becoming such that a city may not 
discharge its sewage into the nearest stream without menacing the rights 
of its own residents, or interfering with riparian rights further down, 
the purification of sewage is a vital matter, and much study has been 
done and many methods proposed and tried in the effort to secure the 
best and most economic results. Chemical precipitation has been exten- 
sively tried and is still used to some extent in connection with other 
methods, but alone it has not been found to be effective. True, clarifi- 
cation can be secured, and much of the organic matter precipitated, but 
enough remains to afford feeding ground for bacteria when the effluent 
happens to again become seeded with them. Moreover, it is not econom- 
ical. Natural methods are now preferred, among which may be men- 
tioned purification by irrigation — a process in which the sewage flows 
over land occupied by growing plants which assimilate a part of the plant 
food carried in the sewage, while another part is purified by nitrification 
in the upper layers of the soil. This method requires extensive area — 
one acre being now regarded as sufficient to purify the sewage of from 
50 to 100 persons, and in the case of a very porous soil of 200, or pos- 
sibly 300 persons. That is to say, that the 998 or 999 parts of water 
carried are sufficient to drown the soil and stop purification of the other 
one or two parts whenever greater quantities are applied to the sewage 
farm. Another objection to the method lies in the fact that in winter 
