94 THE ROYAL SOCIETY OF CANADA 
ually closing in until only a small hole is left through the interior. 
It goes by the name of “ring ice,” but the manner of formation is 
somewhat in dispute by those who have observed it most. From 
appearances the ice seems to be produced by direct freezing of water 
vapor on parts of the pipe interior. Such parts are easily found 
in the coldest rooms where the sprinkler pipe is placed too near the 
refrigerator pipes. Sometimes the sprinkler pipes touches the refriger- 
ator pipes and becomes completely encased in an outward coating 
of hoar frost. In figure 1 is shown a typical case where the sprinkler 
pipe was found frozen solid with ring ice, at a place in the pipe where 
the sprinkler passes close to the ice encased refrigerator pipe. In 
figure 2 is shown an interior view of ring ice formation which was 
photographed by opening the sprinkler pipe. The ice is seen to be 
evenly distributed around the interior of the pipe. 
It becomes a matter of some interest to determine how this 
ice is formed and where the water comes from, in sufficient quantity 
to block many feet of quite large pipe, sometimes two inches or more 
in diameter. 
The most obvious source of water is that carried in by the pump- 
ing of the air into the piping. Another source is to be found in the 
evaporation of the water remaining in the pipes and the freezing 
of this vapor at the coldest points. Yet another source is in the 
water used to prime the valve at the pump house. This priming 
water is on the high pressure side of the system, and the vapor con- 
sequently has free access to the pipe interior. Slow distillation 
must ensue and a gradual accumulation of moisture at the coldest 
points. It must be recognized that this process is slow, but, not- 
withstanding this fact, the time factor runs into months and years 
in many cases, and thus little by little an obstruction of ice may be 
produced. 
By far the most important must be the moisture drawn from 
outside, and pumped into the pipes with the compressed air. This 
has been for a long time recognized by those in charge of installations 
and in some places it is the practice to introduce a drying inlet. Such 
a drying system takes the form of a calcium chloride or lime filter 
where the air is drawn into the pump. A method of drawing the air 
from a cold chamber where the vapor pressure is small, is also used. 
The amount of moisture pumped in will depend chiefly on the 
frequency of the pumping. Suppose the capacity of a sprinkler 
system to be on an average 60 cubic feet, which is about the amount 
of an average installation. During the summer with air at 70° Fahr. 
and 100% humidity there will be in each cubic foot 7-98 grains of 
water vapor at atmospheric pressure. To raise the pressure to 40 Ibs. 
