58 TRANSACTIONS OF THE 
We have then two atmospheres which intermingle but 
slightly. The first below the 10000 m. level. Here we 
have a negative temperature gradient, with the exception 
that below the 3000 m. level in summer time there is oc- 
casionally a positive temperature gradient, that it is hotter 
as one ascends. Then in the upper we have a positive tem- 
perature gradient, freedom from water vapor and no con- 
vectional current. It is physically impossible to have con- 
vectional currents in this layer as a mass of air would be 
continually rising in regions of greater density which is 
not possible. 
IRREGULARITIES WHICH NEED EXPLANATION. 
We have what we call the morning inversion in the 
lower atmosphere, that is the temperature is colder near 
the earth than at the adjacent higher levels. This is due 
to the fact that the earth radiates its heat more quickly 
than does the atmosphere. There are wide changes in tem- 
perature on the earth due to the over and underrunning of 
warm and cold masses of air, and also the amount of insola- 
tion at different points on the surface differ considerably 
due to cloud layers. 
Just the opposite condition prevails during summer and 
winter when a place is under the influence of high and low 
barometer regarding its temperature. 
In summer during high barometer the sky is generally 
clear and conditions are favorable for storing up heat, when 
the barometer is low the sky is overcast and no heat can get 
to the earth and the air is generally cool and below the 
seasonal average. 
In winter, however, during a period of high barometer 
the sky is also clear but the period of sunshine is short, 
radiation takes place freely and it is usually colder than 
during a period of low barometer when the sky is overcast. 
At higher altitudes, however, say 4 kilometers, both in 
winter and summer it is colder during low barometer than 
during high barometer. That is due to the fact that during 
low barometer the air is moist and radiates heat more rap- 
idly than dry air which accounts for the observations. But 
