to Health and Comfort . 
2IX 
1878.] 
pane is supplied by fresh cold air, so that the layer at this 
point approximates to the temperature of the outer air 
closely. On the inside, the layer of warm air in contadt 
with the pane descends as it is cooled, having, perhaps, an 
approximation to the inside temperature at the top of the 
pane, hut by the time the layer has flown downwards to the 
bottom of the pane its temperature will have become mate- 
rially lower than that of air of the room generally. So 
that while the law of mean temperature of the pane at the 
bottom of the pane is yet good, the real temperature may 
he much lower than a simple mean between thermometers 
hung in the room and out of doors. Beside the supposition 
of still air, much allowance must he made for the effedt of 
winter winds in accelerating the flow of cold air on the out- 
side of the pane until the outer layer is very nearly of 
uniform coldness, which favours the greater abstraction of 
heat from the internal descending current, and cools down 
the lower part of the pane still further. Curtains, shades, 
or internal blinds, while they aid in protecting the room 
from loss of heat, also protect the glass from acquiring the 
temperature due to the heat of the room. Until with the 
supposed case of external air at io° above zero, and a mode- 
rate wind out of doors, and of a room warmed to 75 0 inside, 
the temperature of the panes near the bottom, or even well 
up their height, will he much below 42J 0 as the mean ; and 
27 0 to 28° may fairly he taken as giving the real temperature 
near the bottom. This pane of glass becomes, then, a dew- 
point thermometer at all times in the winter, ready for 
indicating the humidity in the air. Except, however, a 
crowd of people, or some artificial “ hydration ” carried 
possibly to momentary excess under the stimulus of the last 
theoriser, or a very new house, or a damp cellar in an old 
one, we but rarely see any indication of presence of moisture 
in our dwellings in cold weather. This simple test will 
show that our dwellings, although the water-troughs of the 
hot-air furnaces do supply limited quantities of vapour with 
admitted comfort, do not, as a rule, have over 30 to 40 per 
cent of humidity in the air within them. 
The entire range of our Atlantic coast is only removed 
from a region of perpetual spring from 200 to 500 miles ; 
and a south-east wind, from December to April, may bring 
a vapour-laden air, which, in a few hours, will have changed 
our frigid winter to a genial spring. The succeeding wave 
of north-west winds — a great current which the Signal 
Service has traced up to the Ardtic regions — may, with 
great violence, restore the winter with all its rigour, within 
P 2 
