486 DOVE ON THE PERIODICAL VARIATIONS 
case; but it is very improbable that, if it exists at all in the 
temperate zone, it attains there the same extent as in Asia; at 
least no trace of it is found in the series of observations for six 
years at Ancaster, between the Ontario and Erie, but a gradual 
rising from June to September, while the five years’ series at 
St. John’s, in Newfoundland, approaches more to Iceland, and 
those at Cambridge in Massachusetts, which are corrected for 
temperature, represent the transition to Europzan relations. 
2. Daily Variations. 
With respect to the influence which the elasticity of the va- 
pour mixed with the dry air exercises upon the extent and course 
of the daily oscillation, we likewise perceive, as in the annual 
variations, that it must differ considerably, according as the place 
of observation is situated near the sea or far from it. For a loca- 
lity of the former description, I have shown by calculation of the 
observations of Appenrade (Poggendorff’s Annalen, vol. xxii. 
p- 219), that in the annual average the daily curve of the ela- 
sticity of the vapour shows no bend at all, but rises uninterrupt- 
edly from the coldest hour of the day to the warmest, and then 
in like manner uninterruptedly decreases ; and that if we calcu- 
late from this the changes of the pressure of the dry air, they lose 
the morning maximum, and follow a period of twenty-four, not of 
twelve hours, and are consequently very closely related to the 
curve of the daily variations of temperature, Since then the ob- 
servations of Plymouth have confirmed this result. But in places 
distant from the sea, where no sea-wind during the day can re- 
store the humidity carried away by the ascending current from 
the lower strata, the elasticity of the vapour will not be able to 
replace what the air loses by thermal rarefaction; we have 
therefore to expect that the morning maximum for the whole 
atmosphere will disappear, just as occurs at places near the sea, 
for the pressure of the air only when separated from the elasti- 
city of the vapour. Now this really happened at Barnaul in 
the years 1838 and 1840 (the year 1839 only shows quite an ir- 
regular course), in Catherinenburg and Nertchinsk, in the mean 
of several years; lastly, at Slatoust the compensation appears 
perfect, while St. Petersburg and Bogoslowsk still exhibit a 
morning maximum. But if we eliminate the vapour, all the 
curves give the determinations found for Appenrade, as shown 
in the following tables (English inch) :— 
