ON THE MAGNETIC INTENSITY OF THE EARTH. 29 
stations. Determinations of intensity in that part of the globe 
: are as yet so rare, that such observations are too valuable to be 
omitted in this memoir ; I have accordingly entered them in the 
general table, as well as in a separate table here, and have an- 
nexed to the latter a brief notice of the manner in which they 
have been computed. 
The last observations recorded in Mr. Douglas’s books are 
those which he made on the dip at Byron’s Bay, and on the 
force, with needles 5 and 6, at Byron’s Bay and in the crater of 
the volcano Kiraueah, soon after his arrival at Owhyhee in 1834. 
I have searched in vain, amongst the few loose papers which 
were sent home, for the rough notes of observations of very 
great interest, of which he speaks in his private letters, but 
which are not entered in his books. I mean those of the dip, 
variation, and intensity at the summit of Mowna Kaah, nearly 
14,000 feet above the sea, andat other elevations on the island 
exceeding 10,000 feet. He mentions, as a general inference’ 
from these observations, that he found little or no difference 
between the three phenomena observed at those heights and 
near the sea. Those in the crater of Kiraueah, about 4000 feet 
above the sea (which are the only ones preserved), indicate a 
decidedly less intensity (1059 to 1°098) than on the sea side at 
Byron’s Bay, a few miles distant: but Kiraueah is a recent 
_ yoleano, and no conclusion, as to the simple effect of elevation 
on the magnetic intensity, can of course be drawn. 
In the first subjoined table are inserted the intensities de- 
termined at the stations where both the dip and horizontal in- 
tensity were observed. The second table contains those sta- 
tions where the horizontal component only was observed, and 
the dips are supplied in the third table according to the expla- 
nation annexed to it. 
Tass I. 
Long. west SS Intensity. London=1°372. 
p Z 
‘om. ae EPR GEOL Ua A EON E 
Greenwich | °Pserved. Nos.3 & 4.) Nos.5 & 6.) Mean. 
a | 
| Fort Vancouver... Nov., 1830... & 37 122 36 
Cape Disap- Sept. Dec., 
sintment } “Hel BRO isco aa 25. 16) #8 56 
Oint George ...]......ssssesseneee 46 11) 123 40 
St. Francisco...... Feb., 1831 ...|37 48| 122 25 
Monterey ......... Jan., 1831 ...}36 35) 122 0 
| Owhyhee ......... Feb., 1834...) 19 43| 156 10 
