of the British Association, to the meeting at Glasgow, 1840. 443 



fulfilment of this important and responsible duty, the Asso- 

 ciation has continued to act upon the principle already laid 

 down in the Address of the General Secretaries at the meeting 

 at Newcastle in 1838, namely, to seek the aid of Government 

 in no case of doubtful or minor importance; and to seek it 

 only when the resources of individuals, or of individual bodies, 

 shall have proved unequal to the demand. The caution which it 

 has observed in this respect has been eminently displayed in the 

 part which it has taken with reference to the Antarctic expe- 

 dition, and to the fixed magnetical observatories. It abstained 

 from recommending the former to the Government until it had 

 called for, and obtained from Major Sabine, by whom the 

 importance of such an expedition was first urged, a report in 

 which that importance was placed beyond all doubt ; and it 

 withheld from urging the latter, although its necessity was 

 fully felt by some of its own members, until the letter of 

 Baron Humboldt to the Duke of Sussex gave authority and 

 force to its recommendation. 



The delay which has in consequence occurred, has been 

 productive of signal benefit to each branch of this great two- 

 fold undertaking. Since the time alluded to, our views of the 

 objects of investigation in terrestrial magnetism have been 

 greatly enlarged, at the same time that they have become 

 more distinct. Major Sabine's memoir on the Intensity of 

 Terrestrial Magnetism has served to point out the most in- 

 teresting portion of the surface of the globe, as respects the 

 distribution of the magnetic force, and has indicated, in the 

 clearest manner, what still remained for observation to per- 

 form; and the beautiful theory of M. Gauss, which has been 

 partly built upon the data afforded by the same memoir, 

 while it has assigned the most probable configuration of the 

 magnetic lines of declination, inclination, and intensity, has 

 done the same service with respect to all the three elements. 



In another point of view, also, delay has proved of great 

 value to both branches ( if the undertaking, but more especially 

 to the fixed observatories. Our means of instrumental re- 

 search have, since the time of their first projection, received 

 great improvements, as well in their adequacy to the objects 

 of inquiry, as in their precision ; and finally, the two great 

 lines of inquiry, the research of the distribution of Terres- 

 trial Magnetism on the earth's surface, and the investigation 

 of its variations, secular, periodic, and irregular, have been 

 permitted to proceed pari passu. 



Last of all, the prudent caution, and vigilant care, which 

 the two great scientific bodies have exhibited, both in the 

 origin and progress of the undertaking, have naturally in- 



