162 THE ANTARCTIC MANUAL. 
mometer of sufficient sensibility combined with a clock movement of 
suitable velocity. Such an instrument draws a sinuous line which is 
generally smooth during the night and serrated during the day. 
The shape and the crowdedness of the teeth on the serrated daylight 
portion of the line have a close connection with, and are to a certain 
extent an indication of, the character of the existing weather. In 
general the indented character of the daylight curve is an indication of 
the disturbing influence of the sun on the equilibrium of the atmo- 
sphere, and this continues just as long as he is above the horizon ; 
after sunset, the atmosphere quickly reverts to a state of greater 
stability.” 
It is only necessary to watch a thermometer during one or two 
minutes to be convinced of the great variability of the temperature 
of the air not only from one minute to another, but almost from 
second to second. This is most easily and most briefly shown by 
quoting the series of observations made at St. Moritz, in the Engadine, 
in February 1894. 
“Jn the winter of this year I revisited the Engadine, and stayed 
for a fortnight at St. Moritz. As the room which I occupied faced 
due north, the window of it was convenient for making observations 
of the temperature of the air. From the 24th February to the 
3rd March I made every morning a series of observations of the tem- 
perature of the air, beginning when there was just light enough to 
read the thermometer, and continuing till between 8 and 9 o’clock in 
the morning. At first I took the temperature every minute, but 
finding the oscillations of temperature very great, I reduced the 
intervals to twenty seconds, and sometimes to fifteen seconds. To 
print the observations im extenso would occupy too much space, 
but the striking features can be easily summarised. They are 
given in Table XXI. Excepting on the 26th February, when 
it was snowing all the morning, the observations embrace the 
interval of an hour or an hour and a half after sunrise. The time 
was devoted entirely to this object, and observations were made 
at as close dates as possible. Working alone, an interval of twenty 
seconds is quite convenient; shorter intervals cause hurry. The 
time immediately following sunrise is when one would expect the 
temperature of the air to rise continuously, if not regularly ; but we 
see that so far from rising continuously and regularly the thermo- 
meter rises, falls, and remains stationary quite irregularly. On some 
days, as on the 28th February, these irregularities are comparatively 
few ; on others, as on the lst and 2nd of March, they are numerous. 
The largest rise or fall in twenty seconds is 0°5 C. From experi- 
