tJ 
ON THE MAGNETIC INTENSITY OF THE EARTH. 27 
» Douglas, 1829-1834,—'These observations were made by. 
Mr. David Douglas during a journey to the N.W. coast of 
America, undertaken for botanical and geographical objects. 
The circumstances of his much-regretted death at Owhyhee in 
the spring of 1834, whilst waiting for a vessel to convey him 
home to England, are too well known to need repetition here. 
Having been supplied with instruments for a part of the scien- 
tific purposes of his journey by the Secretary of State for the 
Colonies, his papers on such subjects were sent by the British 
Consul at the Sandwich Islands to the Colonial Office, and on 
their arrival in England were placed in my hands to examine and 
report upon, The books containing the magnetical observations 
showed, by the completeness of the record, the attention and 
care bestowed on every circumstance which could conduce to 
accuracy. A full report on these, and on his other scientific 
papers, has been presented to Lord Glenelg, the present Se- 
cretary of State for the Colonies, but is yet unpublished. I 
have therefore permitted myself to enter into a more circum- 
stantial account of these observations in this place than I have 
done in regard to other observers, whose works can be imme- 
diately consulted. 
Mr. Douglas was furnished with a dip circle of 11} inches 
in diameter, made by Dollond, with a needle on Mayer's prin- 
ciple ; and for the intensity, with four of the same horizontal 
needles which I had used in 1822-1823, viz., Nos. 3, 4, 5, 6. 
The time of vibration of these needles was observed by Mr. 
Douglas in London, in 1828 and 1829, previously to his leaving 
England. In May, 1830, they were vibrated at Oahu, one of 
the Sandwich Islands; and between September, 1830, and 
February, 1831, at four stations in North America, where 
the dip was also observed, viz., Fort Vancouver, Cape Disap- 
pointment, Monterey, and St. Francisco; and at several other 
stations, where the dip was not observed. In February, 1831, 
he sent Nos. 3 and 4 to England, to have the permanency of 
their magnetism examined ; retaining Nos. 5 and 6 with him 
for further observations. Nos. 8 and 4, from accidental cir- 
cumstances, did not reach me till 1836 in Ireland, and bein 
examined in Limerick and Dublin (both which stations had 
_ been carefully compared with London), No. 3 was found to 
~ have slightly gained, and No. 4 slightly lost magnetism, on a 
_ €omparison with their rates in 1828 and 1829. When not em- 
_ ployed in actual obseryation, these needles were kept together 
in the same case, with their opposite poles connected, as were 
Nos. 5 and 6 in another and a separate case. I have had ocea- 
sion to remark elsewhere, that, when needles differing consider- 
