xLvi DIURNAL VARIATION, &c. 



never before been put to such a test, required the greatest delicacy in its use. When the 

 needle was nicely suspended by a single fibre of New Zealand flax, I found that it was 

 materially disturbed by the approach of any metallic substance, by any sudden increase 

 or decrease of light, and by alteration in the temperature ; if I had a coat with brass 

 buttons, or a watch in my pocket, I saw it move before I was within two yai'ds of it ; 

 nor could I take five successive readings at each end of the needle, without observing 

 that the increase of temperature caused by my looking through the microscopes had a 

 considerable effect, and observing to a second was impossible, the needle having a con- 

 stant tremulous motion. When too dark to observe without a light, I was obliged to 

 take a paper lantern, and even then, when the lighted candle shining through the paper 

 was held for the purpose of reading off the arc, it produced a horizontal motion in the 

 needle, corresponding to the direction and strength of the light. We were now in a 

 position so near the magnetic pole, that the natural or universal magnetic influence was 

 at right angles with a magnetized needle, traversing on a point horizontally, and it was 

 then at liberty to be acted upon by any other influence or power, without restraint, 

 excepting from its friction on that point which was also materially lessened by the 

 power of suspension already described ; and by inspection of the Tables for April and 

 May, 1830, it will be seen that it followed the sun, although protected from its rays by 

 a snow hut covered with canvass, and had it been at the time immediately in the 

 vicinity of the magnetic pole, there could be no doubt but it would have followed the 

 sun completely round the compass. Again, it was, during the winter, when every thing 

 magnetic is more sluggish, proved, that it was disturbed by and followed the light of a 

 candle ; that it was materially disturbed by a brilliant Aurora Borealis, particularly 

 when that was of a deep red. I have therefore concluded, that light, of whatever 

 kind, has the property of combining with the magnetic influence. Of electricity we 

 had no opportunity of making experiments, there being less electric matter in the 

 Arctic Regions than in any other place, as proved on my first voyage, when the elec- 

 trometer was never affected by it. My second conclusion is, that metal of any kind 

 will become iia some degree magnetized, the microscopes became magnetic in June 

 1830, and after the brass instrument made by Mr. Dolland became affected, I sus- 

 pended the needle through a glass barometer tube, and used a paper graduated card, 

 which gave the observation to half a degree, and which, indeed, was as near as its 

 tremulous motion would permit the eye to observe it on a silver arc. My third con- 

 clusion is, that it is affected by temperature. 



So that my observations made during the first voyage were, in that respect, fully 

 confirmed. The following table will clearly show the different periods on which the 

 Diurnal Variation was greatest and least, as well as under what circumstances the 

 differences took place. 



