434 
METEOROLOGICAL OBSERVATIONS 
Cape of Good Hope. — June 1845. 
Standard 
Marine 
Marine below 
Barometer. 
Thermometer. 
Barometer. 
Thermometer. 
standard. 
inches. 
inches. 
inch. 
30-302 
55-7 
30-125 
55-7 
30-195 
58-9 
30-000 
58-6 
30-096 
59-3 
29-933 
59*1 
00 
<43 
i-H 
30-515 
52-4 
30-370 
52-7 
30-097 
54-2 
29-935 
54-3 
30-394 
53-8 
30-225 
53-9 
J 
At the Royal Society’s Rooms, London. — March 1846. 
Standard 
Marine 
Marine below 
Barometer. 
Thermometer. 
Barometer. 
Thermometer. 
standard. 
inches. 
29-548'] 
O 
inches. 
29*390 ] 
inch. 
29-430 I 
29-588 J 
42-5 
29-280 > 
29-450 J 
42-5 
•149 
From these comparisons it would appear that a change of ’05 may have taken 
place in the barometer during the Expedition: as the time is not known when the 
change took place, the mean of the three comparisons, viz. * 1 44 has been applied to 
all the observations. They have also been corrected for the effect of temperature 
on the mercurial column, the corrections being taken from the Table given in the 
Royal Society’s Instructions for Magnetical and Meteorological Observatories, p. 82. 
The daily means thus corrected are given in the Abstract in Table I. 
Table II. contains the means of every seven successive days ; these means have had 
an additional correction applied to them, for the variation in the length of the co- 
lumn of mercury occasioned by the variation of gravity in different latitudes. 
o inch - 
The correction in lat. —20 amounts to — 0*059 
The correction in lat. —45 amounts to — 0*000 
The correction in lat. —70 amounts to +0 059 
and proportionally for intermediate latitudes. 
Table III. contains the general results arranged according to latitude. This has 
been done by grouping together, without reference to date, the weekly means belong- 
ing to nearly similar latitudes. The number of observations, of which each general 
result is the mean, is given in the last column of the Table. 
In order to resolve the heights of the barometer into the two constituents of aqueous 
and gaseous pressure, one of Daniell’s hygrometers was observed at the hours of 
9 a.m. and 3 p.m., by Assistant-Surgeon W. Dixon, M.D., attached to the Expedition. 
The tension of vapour obtained by these observations is taken from the Table in the 
Royal Society’s Instructions (page 89). This being deducted from the height of the 
barometer in Tables II. and III., leaves the pressure of the dry air. 
