_ 
variations of the Magnetic Forces. 333 
ologists as Dove’s theory of the diurnal variations of the barom- 
eter. This theory, as stated by Kaemtz, is that the pressure of 
the atmosphere is equal to the sum of the pressures of dry air 
and aqueous vapor, and thus the barometric column is composed, 
so to speak, of two part. ; ene of which crresponds to the air ; 
the other to the aqueous vapor. Now when the temperature 
rises the density of the air diminishes, but the tension of the 
vapor augments, and vice versa. ‘To bring his theory to the test 
of figures, “he analyzed a set of observations:made by Neuber 
at Apenrade with a Daniell’s hygrometer. He calculated the 
tension of the vapor for each hour of the day, and subtracted .it ° 
tom the barometric column; he thus obtained the pressure ¢ 
‘dry air, and found that it had but one maximum and one min- 
‘sult was obtained from a discussion of the meteorological observ- 
_____ ations made at the Toronto Observatory, during the years 1841 
and 1842. “ The diurnal pressure of the gaseous atmosphere has 
- One maximum which occurs about the coldest hour of the day, and 
_ one minimum which occurs about the warmest hour of the day. 
The elastic force of the vapor has also one maximum which oc- 
curs at 2p. m., and one minimum at 4 a.m. The sum of these 
two pressures however exhibits two daily maxima, viz., at 10 
A.M. and P.m., and two daily minima, viz., about 3 or 4 4. ™. an 
 ?.M. “Thus this knotty question respecting’ the diurnal oscilla- 
ions of the’ barometer has been beautifully resolved by simply 
interrogating natnre.”” A similar conclusion may be drawn 
tom the hourly meteorological observations made during the 
Year 1842 at the following places in Russia, viz., St. Petersburg, 
uraoul, Catharinenburg, and Sitka.* It is true that small irreg- 
ulatities are noticed, but as the same general law appears to exist 
everywhere, it is to be supposed that such irregularities super- 
vene ‘upon it at particular localities by reason of certain local 
peculiarities. 
| 
forms over-compensates this effect, and thus the barometer rises. 
This continues until about 9a. m. After this the diminution in 
the pressure of dry air prevails over the increase due to the aug- 
eS ee Or i et Se iN ree ts Ca 
* See this Journal for January, 1846, pp. 138, 139, 140. 
