¥4 REPORT—1845. 
existence of a diurnal variation in the force of the wind, corresponding in all 
respects with the variation of the temperature. 
Admitting the explanation thus offered to be satisfactory in regard to the 
diurnal variations, it was Obvious that the correspondence of the annual va- 
riations of the temperature and pressures might receive an analogous expla- 
nation. 
A comparison of the results of the observations at Toronto with those of 
the observations of M. Kreil at Prague in Bohemia, (published in the Mag. 
und Met. Beob. zu Prag, and in the Jahrbuch fiir Prag. 1843,) showed 
that the characteristic features of the periodical variations at Toronto were 
not peculiar to that locality, but might rather be considered as belonging to 
stations situated in the temperate zone and in the interior of a continent. 
The annual and diurnal variations at Prague were also single progressions, 
and the same correspondence was observable between the variations of the 
temperature and of the gaseous pressure. 
The publication of the volume of magnetical and meteorological observa- 
tions made at Greenwich in 1842, which took place shortly after the meeting 
of the Association at York; enabled me to add a postscript to the printed 
statement of my communication in the annual volume of the Association 
Reports; showing the correspondence of the results at Greenwich with the 
relations which had been found to exist in the periodical march of the phe- 
nomena at Toronto and at Prague. 
From the concurrence of these three stations, it was obvious that a consider- 
able insight had been obtained into the laws which regulate the periodical 
variations in the temperate zone, and into the sequence of natural causes and 
effects, in accordance with which the annual and diurnal fluctuations of the 
elastic forces of air and vapour at the surface of the earth depend on the va- 
riations of temperature: and from these premises it was inferred, that the 
normal state of the diurnal variations of the pressures of the air and vapour 
and of the force of the wind, in the temperate zone, might be regarded as 
that of a single progression with one maximum and one minimum, the epochs 
of which should nearly coincide with those of the maximum and minimum 
of temperature *. 
* Since this communication was read at Cambridge I have received from M. Dove a copy 
of a paper read to the Academy of Berlin, entitled ‘ Ueber die periodischen aenderungen der 
druckes der Attiosphare im Innern der Continente,’ in which the remarkable facts are stated, 
that at Catherinenbourg and Nertchinsk (on the mean of several years), and at Barnaoul (in 
the years 1838 and 1840), the mean diurnal darometric curve itself exhibits but one maxi- 
mum and one minimum in the twenty-four hours; the maximum coinciding nearly with the 
coldest, and the minimum with the hottest hours of the day. At these stations therefore, 
and in the years referred to, the forenoon maximum disappeared, and the barometrie curve as- 
similated in character to the curve of the dry air in other places in the temperate zone. 
These stations are situated far in the interior of the greatest extent of dry land on the surface 
of our globe, and at a very great distance from an expanse of water, from whence vapour 
can be supplied. The diminished pressure of the dry air produced by the ascending current 
and overflow as the temperature of the day increases, is not therefore compensated by an 
increased elasticity of vapour, and the curve of the diurnal variation of the barometer ap- 
proximates to the form assumed when the elasticities of the vapour at the several hours of 
observation are abstracted. This assimilation in character of the barometric and (inferred) 
gaseous curves, which is thus found to take place in cases where, from natural causes, the 
influence of the vapour is greatly lessened, appears a confirmation of the propriety of sepa- 
rating the effects of the elastic forces of the dry air and vapour in their action on the bard- 
meter. 
M.; Dove considers that the single progression of the diurnal barometric curve, which takes 
place at the three Asiatic stations referred to in this note, is characteristic of a true continen- 
tal climate. Itis, without doubt, characteristic of an extreme climate, and as such is highly 
instructive. There appears reason to doubt whether an extreme climate of corresponding 
character exist at all in the temperate latitudes of the continent of America. 
If, however, we examine the record of the observations made hourly in the year 1842 at 
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