1895-96.] Dr J. Halm on the Temperature of the Air. 
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Theoretical Researches on the Daily Change of the 
Temperature of the Air. By Dr J. Halm. (With a 
Plate.) 
(Read July 20, 1896.) 
I have the honour to lay before the Royal Society a short 
account of some theoretical researches on the daily change of the 
temperature of the air, made by me in 1895, and published to 
a certain extent in the Nova Ada der haiserlich Leopoldinisch- 
Carolinischen Academie der Naturforscher, Band lxvii., No. 2. 
Some more recent investigations on the subject, chiefly dealing 
with the physical point of view of the problem, have not yet 
been published, but seem to me of such importance as to j ustify 
me in presenting a brief sketch of them to the Society in this 
paper. 
The history of the mathematical aspect of the problem can be 
traced back as far as the middle of the last century, when Lambert 
made the first attempt at investigating the relation between solar 
and terrestrial radiation and the temperature of the atmosphere. 
He was succeeded by a great number of famous mathematicians 
and meteorologists, whose labours, however, though they con- 
tributed considerably to our knowledge of certain parts of the 
question, have not been rewarded, it must be said, with any sufficient 
result; so that a satisfactory solution of the problem by means 
of theoretical investigations has been eventually considered impos- 
sible, at least in some quarters. 
There can be no doubt that, in a problem like this, an immense 
number of different errors affect the principal conditions of the 
propagation of heat, which conditions are supposed to be the 
causes of the observed changes of the temperature. The clouds, 
which alter the quantity of solar heat radiated towards the surface 
of the earth, the aqueous vapour continually changing its amount 
in the atmosphere, the convection currents carrying heat from the 
soil to the upper layers of the air, and allowing colder atmospheric 
elements to come into contact with the thermometer, the wetness 
