54 REPORT—1840. 
which I will simply indicate: first, that by its nature the 
absorption of heat due to direct radiation from the sun must go 
on more rapidly than the dissipation of it by cooling; and 
secondly, that some influence may be attributed to the different 
distribution of vapour during the rise and decline of tempera- 
ture. 
43. Owing to these causes, thermometric curves, if they can 
be assimilated to symmetric geometrical curves at all, such as 
parabolas, must be regarded as having their axes oblique and 
not vertical. An erect parabola cannot even, generally speak- 
ing, be employed for finding the maximum with exactness on 
this account. But, in point of fact, no one parabola can repre- 
sent all the parts of the thermometric curves which, in their 
least complicated forms, approach more nearly to the curve of 
sines. 
44, From the tables of Brandes and others, we may infer 
the probability of discovering special inflections of the annual 
curve which characterize particular regions of the globe. The 
European curves point, for instance, with great distinctness to 
a check in the progressive rise of temperature, owing to the 
increasing power of the sun, which occurs almost invariably in 
the middle of February. This inflection of the annual curve, 
which in Europe always bends it towards horizontality, and 
sometimes produces distinctly a second minimum in March, is 
a circumstance which has attracted too little attention, and as 
an indication of other general inflections deserves notice. This 
circumstance has lately been insisted on by M. Erman, in a 
letter to M. Arago*, who ascribes it, I think, with unwarrant- 
able boldness, to the interception of the solar rays by the pas- 
sage of the meteors of November between the earth and sun! 
I believe that it can be very easily accounted for, as occurring 
in Europe (which is all we know at present), by the periodic 
easterly winds of spring, caused by an unequal effect of tem- 
perature which we shall presently notice, and which almost 
invariably set in for a time at that season, bringing masses of 
cold air, from the continental regions of Europe and Asia, to 
the western shores +. 
* Comptes Rendus (Paris), x. 21. (1840.) 
¢ Since these pages were written, I have received from Prof. Dove of Ber- 
lin his elaborate Memoir “ on the non-periodic changes of the Distribution of 
Temperature on the Earth’s Surface,” in which he has collected the most com- 
plete series existing of authentic observations of monthly mean temperature 
for fifty-nine stations. One of his conclusions is remarkable, viz. that when a 
large portion of the earth’s surface is taken into view, the apparent irregularities 
of particular seasons counteract one another, so as to give no countenance to 
the idea, that more heat falls on the earth generally one year than another. 
