PASTEURIZATION. 181 
would have the same resistance to heat as a layer of copper 
2 meters in thickness. Consequently a very thin layer of water 
or condensed steam on the sides of the heating-wall would 
greatly interfere with the economic efficiency of a pasteurizer. 
In order to overcome this difficulty drip-rings were circled 
round the drum of the pasteurizer at intervals on the steam side 
of the heating-surface. The first rings put around the pasteurizer 
were narrow smooth bands. These did not give entire satisfac- 
tion, as the condensed water from the top rings would drip on 
the edge of the lower ones, and cause the water to splatter over 
the side of the heating-wall. Another kind of ring was then in- 
vented, which 
was thin, nar- 
row, and saw- 
teeth-like in & 
shape. These © 
rings were fast- 
ened to the 
heating-wall at 
proper _ inter- 
vals at an angle 
of 45°. The 
rings were so 
arranged that 
the drops of condensed water escaping from the end of each saw 
tooth would fall in the hollow between the teeth in the lower rings 
and thus prevent any splattering of the water against the heating- 
wall. These contrivances greatly increased the efficiency—as high 
as 48°%,—and the capacity of the pasteurizer experimented upon. 
(4) Difference in Temperature on Each Side of the Heating- 
surjace.—The difference in the temperature on each side of the 
heating-surface has a great effect upon the rapidity with which 
the heat passes through the wall. The lower the temperature 
is on the milk side the more rapidly does the heat pass through; 
and the higher the temperature of the milk is, the pressure on 
the steam side being the same, the more slowly the heat passes 
through the heating-wall. This would at first lead us to be- 
The Farrington pasteurizer. 
