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. a - Proceedings of the British Association. 
surrounding districts. It is only by reference to such central 
Stations as zero points, that itinerant determinations can be di- 
“vested of the influence of temporary and casual magnetic de- 
rangements, and brought into comparability with the general 
magnetic system of the globe. It is, therefore, of the utmost 
importance, that every advantage should be taken of the present 
fortunate conjuncture to secure the whole benefit of the simulta- 
neous system, and to extend it from points over districts. | Itine- 
rant observations, made on a connected system, and precisely si- 
multaneous with those at fixed observatories, will acquire, (if ac- 
curately made,) all the value of stationary ones, becoming ipso 
facto, and at each instant, reducible to a central station. More- 
over, by this means alone can the amount of station error for each 
element, at the central stations themselves be ascertained ; by 
which is meant, all that part of each resolved element of the mag- 
netic force, which not being participated in by the surrounding 
district, must be attributed to attractions merely local and acci- 
dental. Without such surveys, executed at some epoch, this 
error cannot be even approximately fixed. If executed at this 
particular time, not only will it be settled with precision, but the 
surveys will become an independent part of the whole mass of 
observation, and be rendered. infinitely more valuable as data for 
future reference, than they could possibly be if deferred till after 
the conclusion of the stationary observations. 
Under this impression it is highly gratifying to your comicaitiele 
to be enabled to announce that one very important survey of this 
kind,—that of the British possessions in North America—has, on 
Hpeimpplicetion of the Beesident and Council of the Royal Soci- 
, on a scale both liberal and 
tnlinlactory--n young, — and instructed officer, Lieut. Young- 
husband, R. A., qualified for the work by a residence and prac- 
tice in magnetic observation in the observatory at Toronto,— 
having been added to the establishment of that observatory, with 
a view to this especial service, for three years, with a non-commis- 
sioned officer as his assistant, furnished with every instrumental 
requisite, a liberal provision for travelling expenses, and with the 
promise of gratuitous canoe conveyance, from the Hudson’s Bay 
Company = the territories. belonging to them.. In anticipation, 
South Africa, though 
e1rptrroatr 
; ar ni y 
as ye no formal applic iti n-for such a survey has been made, the 
ae tee 
