I 
REPORT ON METEOROLOGY. 229 
the effect of air in his barometer, which, considering the variable 
temperature to which it must have been exposed, rather dimi¬ 
nishes our confidence in the observation. Captain King com¬ 
municated to me a remarkable barometric anomaly observed 
by him at Port Famine in the Straits of Magellan. The instru¬ 
ment was compared with that at Greenwich on leaving and on re¬ 
turning to this country, and was observed five times a day, with 
all care, for five consecutive months. The result gave the very 
small mean height of 29*462 inches at five feet above high-water 
mark*. This fact seems intimately connected with those just 
mentioned. 
The variations of pressure may be considered as periodical 
and accidental. 
Of the periodical variations, that which first demands our 
attention is the horary oscillation. This phenomenon, some¬ 
what indistinctly pointed at by observers in the tropics above 
a century ago, has within the last thirty years acquired great 
interest. Baron Humboldt by his observations near the equa¬ 
tor gave an impulse to inquiry, and the observations have been 
pursued with assiduity and success throughout a great range 
of latitude. The general fact that the barometer attains a 
maximum in the tropics at 9 a.m. and p.m. and a minimum at 
3 or 4 a.m. and p.m., it must be hardly necessary to recall. 
Nor does it fall within our province to recapitulate the labours 
of Ramondf, or the individual results of the earlier observers. It 
is sufficient to mention the well-known names of Humboldt, Cal- 
das, Horner,Boussingault and Rivero,and Simonoff, as observers 
in the tropics ; and of Marque-Victor, Billiet, Gambart, and 
Herrenschneider in Europe. Of the recent contributions which 
fall more particularly under our notice, M. Bouvard’s Memoirs 
are the first. In an excellent analysis of the meteorological 
observations made at Paris J, he has determined with great ac¬ 
curacy the amount at that station, which gives for the morning 
period 0*76 millimetre, and for the evening 0*37, by the mean of 
eleven years. In a later paper he has analysed the law of dimi¬ 
nution of the oscillation from the equator to the poles, and likewise 
the influence of height and of seasons §. Helias adopted the Table 
given by Humboldt in his admirable Essay on this subject j|, and 
enlarged it by new observations, especially the manuscript ones 
* The results have been published, hut without any remark, in the first 
Number of the Royal Geoyraphical Society's Journal, p. 172. 
+ Memoires de V Institut, 1812 ; and his excellent Memoires sur la For mule 
barometrique de la Mecanique Celeste. 
X Memoires de VInstitut pour 1824. § Bibliotheque Universelle,\$29, 
|| Relation Historique, 4to edit. tom. iii. 
