BACTERIOLOGY OF ICE 335 
inated with typhoid baclh. Watt (1918) reported that three weeks’ 
treatment of river water with three parts of lime per 100,000 reduced the 
number of B. colz and gave generally satisfactory results with the excep- 
tion of a slight coloring and increased alkalinity. This investigator 
recommends the “‘ excess lime method ”’ as satisfactory for epidemics of 
typhoid fever where it is necessary to quickly improve the water supply. 
TABLE XXX 
CHEMICAL ANALYSIS: IN PARTS PER MILLION WITH THE ACTION 
OF LIME-TREATED WATER ON TYPHOID BACTERIA 
(Hoover and Scott, 1914) 
BacrERIAL ANALYSIS OF 
Total \Biearbonat Normal Excess Softened Water jnocu- 
O , 1912 ova warponate Carb t Ime ated Wl ypnol 
et Alkalinity | Alkalinity Alkalinity A Gaustre Softened ; Baerlli 
Control 
20 47 5 42. 0 0 180 0 
21 52 8 44 0 0 20 0 
23 59 7 52 0 0 50 6 
24 58 12 46 0 0 165 2 
25 64 8 56 0 0 390 0 
25 58 2 56 0 0 360 1 
26 50 2 48 0 14 3600 1 
28 46 0 42 4 0 300 0 
29 48 0 48 0 1 3600 0 
BACTERIOLOGY OF Icz 
The harvesting of natural ice and the manufacture of artificial ice 
have become well-established industries. The growth of large metro- 
politan centers which are well removed from the source of food supplies 
and rural districts, have made these industries important ones. 
Kinds of Ice. There are two kinds of ice, artificial and natural. 
Natural ice 1s secured, in the northern chmates, from natural bodies of 
water. It is cut into blocks which are convement for handling and 
delivered to the consumer after storage. Such ice may be contaminated 
either from being taken from too badly polluted bodies of water or by 
being handled in an unsanitary manner. 
Artificial ice is produced mostly by the can, method. ‘These are 
usually about the: size of an ordinary cake -and, "before freezing are 
