NOTES ON THE PROLONGED FROST, 1890-91. 65
fall of snow from December 10th to January 19th inclusive corresponded to .81 in.
of rain.
During the whole period there was fortunately but little wind. A force of 3°
was the maximum registered, and that on one occasion only, and most of the time
easterly winds prevailed.
Chart showing Mean Temperature and Minimum Temperature each Day during
Prolonged Frost of Winter of 1890-91.
Thick (upper) line Mean Temperature for day; thin (lower) line Minimum Temperature
for day.
As for some weeks there was only a thin covering; of snow on the ground, the
effect of the continued cold will probably have proved very disastrous to vegetation
Some of our members who are interested in agriculture will probably have some-
thing to say on this point.
The effect of the prolonged frost on water mains :—No observations were taken
of the earth temperature at varying depths, though such a series would be very
interesting. What that temperature was, however, can be judged from its effect
upon the Chelmsford water mains.
The water in the more superficial mains was frozen before Christmas, and
before the break up of the frost the mains at a depth of two feet had become
affected. This of course caused great inconvenience in many parts of the town,
and it was some time after the thaw had set in that the ice in such mains melted.
When this occurred the havoc wrought by the expansion of the water in the
act of freezing became apparent. The mains had been fractured in most diverse
ways and to varying extents and water was rushing to waste at numbers of
places.
The moral of this experience is that water mains should be laid at a greater
depth than is frequently the case. The slight additional first cost of adopting
such a course is as nothing compared with the great inconvenience, annoyance
and damage wrought by a single severe frost when the pipes are too superficially
bedded.