C 73 3 
III. Magnetical Observations at Port Bowen , &c. A. D. 1 824-25, 
comprehending observations on the diurnal variation and 
diurnal intensity of the horizontal needle ; also on the Dip of 
the magnetic needle at Woolwich , and at different stations , 
within the Arctic circle . By Captain W. E. Parry, F. R. S. 
and Lieutenant Henry Foster, F. R. S. 
The daily variation of the horizontal needle was first ob- 
served in London by Mr. Graham, in the year 1722; but 
in consequence of its small amount, it has always been con- 
sidered amongst the minor phenomena which the magnetic 
needle presents. Mr. Barlow, however, having explained 
a method of encreasing the amount of this daily change very 
considerably, in any latitude,* this phenomenon began to as- 
sume a different character, and seemed to furnish a subject 
of highly interesting, if not of useful, enquiry. 
Therefore, soon after our arrival at Port Bowen, an attempt 
was made to obtain the diurnal variation of the magnetic 
needle at this place, with an instrument constructed by Mr. 
Dollond for that purpose, and which had been used at the 
Whale Fish Islands. But the weight of the needle occasioned 
so much friction on the point of support, that no movement 
could be detected ; and after several trials, which it is un- 
necessary here to detail, (and in the course of which it was 
discovered that the brass composing the instrument was in 
every part highly magnetic) it was wholly laid aside as use- 
less in these latitudes. 
mdcccxxvi. 
* Phil. Trans, for 1823. 
* L 
