Ross.—On the Declination of the Magnetic Needle. 5 
this phenomenon by myself, I should have been disposed to receive with 
caution the evidence even of my own senses as to this last fact; but the 
appearance conveying precisely the same idea to three individuals at once, all 
intently engaged in looking towards the spot, I have no doubt that the ray 
of light actually passed within that distance of us. About one o'clock on the 
morning of the 23rd February the aurora again appeared over the hills in а 
south direction, presenting a brilliant mass of light very similar to that just 
described. The rolling motion of the light laterally was here also very 
striking, as well as the increase of its intensity thus occasioned. The light 
occupied horizontally about a point of the compass, and extended in height 
scarcely a degree above the land, which seemed, however, to conceal from us a 
part of the phenomenon. It was always evident enough that the most 
attenuated light of the aurora sensibly dimmed the stars, like a thin veil drawn 
over them. We frequently listened for any sound proceeding from this 
phenomenon, but never heard any." 
Now let us see what Captain Parry says in reference to the action of his 
compasses during the continuance of this phenomenon:— Our variation 
needles, which were extremely light, suspended in the most delicate manner, 
and, from the weak directive energy, susceptible of being acted upon by a very 
slight disturbing force, were never in a single instance sensibly affected by the 
aurora, which could scarcely fail to have been observed at some time or other, 
had any such disturbance taken place, the needles being visited every hour for 
several months, and oftener when anything occurred to make it desirable." 
I believe that the officer in charge of the Dunedin Telegraphic Station has 
generally observed, on the day preceding a display of aurora, a considerable 
disturbance in the needles attached to his instruments. Those needles are, 
however, placed under very different conditions to those to which the needle 
of a declination compass would be subject ; and whilst a current of induced 
electricity may perhaps (independent of the battery) be directed along the 
copper wire, which is in close proximity to the telegraph needle, and in 
accordance with the established law that “electrical force and magnetic force 
are exerted at right angles to each other,” deflect it from its normal position, 
the isolated declination needle may remain unaffected, or affected only in a 
slight degree. 
In addition to the secular, annual, and accidental variations of the 
declination, there are also local variations. Within our own Province of Otago 
there are many such, some of them of a very remarkable character. 
The secular variation in the “declination” of the needle, as nies hae 
from astronomical observations taken on board ship, in the vicinity of our coast 
line, is stated on the Admiralty charts to be progressing in an easterly direction 
at the rate of nearly two minutes per annum. 
