216 ON DETERMINATIONS OF THE ABSOLUTE VALUE, SECULAR CHANGE, 
magnetic elements at Toronto and Hobarton to state ; — that in the months from 
October to February the magnetic needle more nearly approaches the vertical direc- 
tion at both stations, and from April to August the horizontal direction ; — and that 
the total force is greatest at both stations from October to February, and least from 
April to August. 
It is much to be desired that so remarkable a result should receive a full con- 
firmation, by the continuance of the observations at Toronto and at Hobarton for such 
an additional period as may appear necessary for that purpose ; and that the general 
conclusion indicated by the observations at those stations should be verified by simi- 
lar investigations in other parts of the globe, especially at the observatories which 
now exist. The facts, as far as they go, indicate tlie existence of a general affection 
of the whole globe having an annual period, and would appear to conduct us natu- 
rally to the position of the earth in its orbit as the first step towards an explanation 
of the periodic change*. It might possibly be regarded as premature, in the present 
stage of the inquiry, to enter on the discussion of such physical hypotheses as may 
present themselves on the supposition of a causal connection of this nature ; but it 
cannot be open to the same objection, to press on the consideration of those who are 
engaged in experimental researches in terrestrial magnetism, (or of others who may 
have it in their power, from station or influence, to give countenance or support to 
those who are so engaged), the importance of following up without delay, and in the 
most effective manner, a branch of the research which gives so fair a promise of 
establishing a conclusion of so much theoretical moment upon the basis of competent 
experiment'!'. 
I may be permitted, in conclusion, to advert, though very briefly, to considerations 
which may give a particular importance to accurate numerical values of the magnetic 
elements and their secular changes determined at Toronto. 
That station was selected on account of its proximity to one of those remarkable 
points on the globe which have a peculiar importance in theoretical respects : viz. to 
one of the two points in the northern hemisphere which are the centres of the loops 
* The portion of the year when the magnetic force is greatest and the direction of the needle most vertical 
in both hemispheres, viz. from October to February, coincides with that in which the earth is nearest to the 
sun, and also moves with greatest velocity in her orbit. There is another curious annual coincidence of a 
wholly different nature, unconnected with the position of the earth in her orbit ; during the months from Oc- 
tober to February, when the magnetic force is greatest and the direction of the needle in both hemispheres 
most vertical, Mr. Dove’s recent investigations have shown that, owing to meteorological causes traceable to 
the unequal distribution of land and sea in the two hemispheres, the aggregate temperature of the whole earth 
is lower than in the opposite period of the year. 
t I am glad to be able to add, that by a letter received from Lieut. Gilliss of the United States Navy, 
Director of the Astronomical Observatory established at Santiago in Chili, magnetical observations, similar to 
those referred to in this communication as being in progress at Toronto and Hobarton, were commenced at 
Santiago in January of the present year, with instruments which had been prepared at Woolwich at the ex- 
pense and by the request of the Government of the United States. 
