296 
TYPHOID FEVEE IX DISTEICT OF COLUMBIA. 
freezing, and tlie ice, even if kept for a considerable period after 
manufacture, fail to show any cbeniical evidences of such pollution. 
On the other hand, it is conceivable that a polluted water might after 
freezing show chemical evidences of pollution and yet be practically 
sterile, for the reason that the substances indicating pollution are not 
destroyed by freezing and may persist in the water (or ice) long after 
the bacteria causing these changes have perished. Hence it is that 
among a considerable number of samples of ice we might expect to 
encounter a greater number of discrepancies between the chemical 
and the bacteriological finchngs than among an equal number of speci- 
mens of water, and such has been our experience. 
WELLS IX USE BY THE ICE FACTOEIES OF THE DISTEICT OF COLLTMBLi. 
The present investigation has also included the bacteriological and 
chemical examination of the waters of 21 wells which are used for one 
purpose or another in the various ice factories now in operation in the 
District of Columbia. According to the statements of the manii- 
facturers the waters of these wells, in most instances at least, are 
employed only for purposes of condensation and not in the manu- 
facture of the ice itself. The use to which the water of any particular 
well of this series is put is indicated in the colunm headed '^Remarks” 
of the table p. 105 of this report. The results of our bacteriological 
and chemical examinations of the waters of these wells are also given 
in this table, from which it may be seen that so far as chemical evi- 
dences of pollution are concerned, the waters of this group of wells 
mav be classified as follows: 
No. of 
sample. 
251. 
252. 
255. 
256. 
257. 
272. 
273. 
295. 
PURE . 
Hygienic Ice Company, Fifteenth, and E streets XE. 
Hygienic Ice Company, Fifteenth and E streets XE. 
Hygienic Ice Company, Fifteenth and E streets XE. 
Hygienic Ice Company, Fifteenth and E streets XE. 
Hygienic Ice Company, Fifteenth and E streets XE. 
Purity Ice Company, Fifth street market XIV. 
Purity Ice Company, Fifth street market XW. 
Corby Company, Langdon, XE. 
REMOTE POLLUTIOX. 
238. Home Ice Company, Tvelfth and Y streets XW. 
240. Home Ice Company, Twelfth and V” streets XW. 
241. Home Ice Company, Tweh’th and V streets XW. 
253. Hygienic Ice Company, Fifteenth and E streets XE. 
254. Hygienic Ice Company, Fifteenth and E streets XE. 
266. Auth Provision Company, Seventh and Yhginia avenue SW. 
