153 



probably determinable only by observations at places even more dis« 

 tant from each other than those now embraced in the German series. 



The invention of an instrument by Gauss, for determining the changes 

 in horizontal magnetic intensity with the same accuracy as those of 

 the direction of the needle, will give rise to interesting developments 

 in regard to them; and the changes of the three elements of horizontal 

 direction, and horizontal and vertical intensity are all included by the 

 two instruments before referred to, and a third invented by Professor 

 Lloyd, of Dublin. It is the object of the series now projected, to em- 

 brace these three elements; to extend the number of stations with 

 special reference to their distribution at points of the earth interesting 

 in their magnetic relations ; to keep up a constant series of simulta- 

 neous observations for three years; and thus to effect, on an extended 

 scale, what the German Magnetic Association has so well begun. 

 The execution of this plan, with observations of an appropriate kind, 

 directed also to magnetic research, by a naval expedition, was recom- 

 mended to the British Government by the members of the British 

 Association, including men of science from different countries, in 

 1838. It subsequently received the sanction of the Royal Society 

 of London, was adopted by the Government, and is now in course 

 of execution. It may be considered, therefore, to have been ap- 

 proved by the highest scientific authorities. In pursuance of this 

 plan, stationary observatories are to be established, and regular obser- 

 vations made, for the next three years, at Toronto in Upper Canada, 

 at St. Helena, at the Cape of Good Hope, and at a station in Van 

 Dieman's Land. The East India Company have also undertaken to 

 furnish the means of observation at nine points in their dominions. 

 European Governments, who have not hitherto joined in the German 

 system, with which this will be in connexion, have also promised 

 similar aid. It is this extended scheme, to which our attention has 

 been specially invited by a circular from the Royal Society of Lon- 

 don, and in which the American Philosophical Society desires that 

 our country should co-operate. It is on a broad scale, worthy of all 

 encouragement, and the magnitude of the scheme, the objects for 

 which it is undertaken, and the possibility of its execution, all mark 

 the character of the period in which we live. 



The Society would propose, in furtherance of this plan, that five 

 magnetic observatories should be established in the N. E., N. W., 

 S. E., S. W., and at some central point of the United States, furnished 

 with the instruments and observers necessary, fully to carry out the 



