and Intensity of the Magnetic Needle. 349 



was at a distance from the ships, in order that the needles should 

 be out of the influence of the iron on board ; and that, not- 

 withstanding these obstacles, the needles were carefully watch- 

 ed, the experiments performed, and the results carefully regis- 

 tered every hour, and frequently oftener, during this whole pe- 

 riod ; we shall feel convinced, that more than common exertions 

 were made, and more than usual interest must have been excit- 

 ed, in the pursuit of these curious and valuable experiments ; 

 and, if we add to this, that these energies and these means ^were 

 employed in a situation where Nature has placed her great depot 

 of magnetic powers, and where every phenomenon of this kind 

 is exhibited on the grandest scale, we shall then, and not till 

 then, sufficiently appreciate the value of these interesting and 

 important results. 



With this feehng, 1 have thought that a brief abstract of 

 these experiments would be acceptable to many of the readers 

 of the Edinburgh Journal, particularly to those who have not 

 the opportunity of consulting the original memoir ; and I have 

 accordingly, in the following pages, endeavoured to convey 

 within the least compass, a general view of the subject, and have 

 ventured also upon one or two illustrations of some of the theo- 

 retical points touched upon by the authors of the papers in 

 question. 



The first of the magnetic articles is by Lieutenant Foster, from 

 which it appears, that, previous to his leaving England, he had de- 

 termined upon making a series of observations on the daily varia- 

 tion of the magnetic needle, when any opportunity offered of so do- 

 ing J and the first occurred at Whale Fish Islands, during the time 

 of trans-shipping the stores from the transport which had accom- 

 panied the expedition to that place. The time employed in these 

 experiments was only three days, consequently the results are not so 

 certain as we could wish ; but it is satisfactory to find, that the few 

 facts which were obtained agree remarkably well with each other, 

 both as to quantity and to the time of the day when the variation 

 was the greatest westerly, — the least westerly variation, or the maxi- 

 mum of "Easterly variation, occurred during the night, and was not 

 observed. The greatest daily variation westerly was 23', and this 

 occurred at 1*^ 10' p. m., at which time the sun was west by compass, 

 the mean variation being 70° 2' W., and dip 82° 5S' W. The im- 

 portant remark, distinguished above by italics, seems to have been a 

 strong incitement to Lieutenant Foster to prosecute the subject 

 again on a larger scale the next favourable opportunity, which did 

 not occur till the ships were laid up for the winter at Port Bowen. 

 At this place, as we have already stated, the experiments were be- 

 gun on the 10th of December 1824, on one needle only. In the 



