154 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 comparabihty 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 lohole 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 committee 

 to be enabled to announce that one very important survey of this 

 kind, — that of the British possessions in North America — has, on 

 the application of the President and Council of the Royal Soci- 

 ety, been undertaken by government, on a scale both liberal and 

 satisfactory — a young, ardent 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 oflicer 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, in the territories belonging to them. In anticipation, 

 moreover, of a similar magnetic survey of South Africa, though 

 as yet no formal application for such a survey has been made, the 



