1895 - 96 .] Dr J. Halm on the Temperature of the Air . 
267 
but, considering the fact that only the outmost superficial parts 
contribute to the radiation, and that these very soon get dry by 
great. However, it must exist, and it is very satisfactory to find 
that the observations, as we shall see, show this small difference in 
the theoretical equations in an extraordinary manner. On the 
other hand, we must also take into account that most of our 
meteorological stations are near houses, roads, etc., the specific heat 
of the stonework of which is certainly less than the average, and 
not exceeding 020. 
Hence, if it is permissible to speak of an average value of the 
specific heat of the soil at all, we have strong reasons to suppose it 
practically identical with that of the atmosphere. So, putting 
The equations in this form are not new ; they were given more 
than twenty years ago by A. Weilenmann in the Meteorologische 
Zeitschrift for 1873, and especially in a most interesting paper, 
“Ueber den taeglichen Gang der Lufttemperatur zu Bern,” an 
attempt to theoretically represent the curve of the air temperature 
during the night. But, unfortunately, he did not succeed in 
giving a sufficient explanation of his mathematical terms, nor was 
he able to extend the theory to the principal and more interesting 
part of the daily curve, that between sunrise and sunset. Never- 
theless, great merit is due to him for having first propounded these 
equations, which not only represent practically the whole daily 
curve of temperature after a proper application of the law of solar 
radiation in a most perfect way, but give answer to questions con- 
cerning some conditions of our atmosphere till now unsolved, as 
well as to the last and most important theories on the periodicity 
of solar heat. 
the perpetual process of evaporation, this influence cannot be very 
c L = c 2 and — — h, 
we arrive at our final system of equations : 
