Chemical examination of the water supply. 295 
factory, so that it is no uncommon thing to find specimens of manu- 
factured ice containing free ammonia in such quantities as to impart 
a distinctly alkaline taste. Such being the case the presence of large 
amounts of free ammonia in manufactured ice is no evidence of pol- 
lution. On the other hand, specimen No. 12 is a manufactured ice 
which is evidentl}^- made directly from the water of one of the shallow 
wells in this locality. This particular sample of ice is, according to 
the chemical results, polluted and unfit for anything except general 
cooling purposes where it is not brought into immediate contact with 
drinking water or food. It should also be observed that this particu- 
lar sample, like the water of many of the shallow wells showing chem- 
ical evidences of pollution, contained very few bacteria per cc. As 
has been found, however, with many waters of the shallow wells the 
chemical analysis points unmistakably to pollution, and the same con- 
siderations which have led us to recommend the abandonment of all of 
the shallow wells throughout the District would also lead us to con- 
demn the practice on the part of ice manufacturers of making ice 
directly from the water of such wells. Besides specimen 12, speci- 
mens 9, 16, 28, 30, 32, and 33 contained larger quantities of nitrites 
than might be expected in pure ice, and specimens 6, 8, 13, and 29 
contained quantities of albuminoid ammonia either closely approxi- 
mating or slightly exceeding the limit assigned by Wanklyn and 
Chapman, viz, 0.08 parts per million for a safe water. Three speci- 
mens of the ice showing large quantities of albuminoid ammonia, viz. 
Nos. 8, 13, and 29, were also found by the bacteriological examina- 
tion to be either polluted or suspicious, while No. 6 according to the 
bacteriological findings was of good quality, and similarly no evi- 
dences of bacterial pollution were found among those specimens 
showing large amounts of nitrites. On the other hand a number of 
specimens showing no chemical evidences of pollution were found as 
the result of the bacteriological examination to be suspicious or pol- 
luted. Such was the case with specimens 1, 2, 5, 7, 10, 14, 26, and 34. 
This lack of agreement between the chemical and bacteriological 
findings in the case of these several specimens of ice is doubtless to be 
accounted for in the following manner: It is probable that the speci- 
mens of ice showing bacterial contamination, but giving no chemical 
evidences of pollution, really received their bacterial contamination 
through uncleanliness and careless handling, either immediately 
before, during, or after freezing, in which event while the organisms 
or at least a certain number of them might remain alive, their growth 
and development would be so interfered with at this low temperature 
that the products of their life and growth would not accumulate in the 
ice in sufficient amounts to give chemical evidence of pollution. In 
this way a pure water might become seriously contaminated bac- 
terially, either immediately before or during or immediately after 
