488 DOVE ON THE PERIODICAL VARIATIONS 
D. Nertchinsk. 
Elevation of 
Barometer. | the vapour. Dry air. Temp. R. 
8 | 27-7120 | O51 | 275610 | —5-030 | 
10 ‘7105 | 0-172 5385 | —3:160 | 
12 7080 | 0-193 5150 | —1-640 | 
2 7045 | 0-209 4955 | —O-615 | 
4 | +7038 | 0213 | -4908 | —0-680 | 
6 7040 | 0-202 | +5020 | —1-365 
8 7063 | 0-185 | 5213 | —1-470 
10 7093 | 0-176 5333 | —3-595 
Ose. | 0-0082 | 0-162 00702 | —4-415 
On the whole, we perceive a perfect parallelism between the 
annual and daily periodical variations, a surprising simplification 
of a most complicated phenomenon, as soon as we separate the 
pressure of the dry air from the elasticity of the vapours. But 
in like manner, as the periodically varying direction of the wind 
exercises an influence, however small, upon the annual oscilla- 
tions, there may exist co-operating causes for the daily changes, 
which have not been taken into account in the present investiga- 
tion*. But whatever explanation we may give of these causes, 
the fact of that simplification is established and confirmed by 
observations extending from England to Nertchinsk, and no 
theory of these phenomena can disregard it. It is an essential 
part of the phenomenon itself. 
To enter into a similar examination for the tropical regions 
would be most important for the explanation of the phanomenon. 
From the constant direction of the trade-wind, a separation of 
the dry air and the vapour-atmosphere appears less requisite 
there; but this can only be decided when we can compare a 
place of the continental climate to one of the sea-climate within 
the tropics also. This however will probably long remain a vain 
wish. 
* I have entered more largely into some of them in a former treatise (Annalen, 
vo]. xxii. p. 219). As hourly observations are now making at several Russian 
stations, a more strict investigation of the present problem will be possible at a 
future period. 
