ON MAGNETICAL ANf) METEOROLOGICAIi OBSERVATIONS. 143 



Si:Fth Report of the Committee, consisting of Sir J. Herschel, the 

 Master of Trinity College, Cambridge, the Dean of Ely, 

 Dr. Lloyd and Colonel Sabine, appointed to conduct the co- 

 operation of the British Association in the system of Simulta- 

 neous Magnetical and Meteorological Observations. 



In the arrangement of the subjects of this report, the plan of former reports 

 having been found convenient will be adhered to ; — and first respecting the 



Antarctic Expedition. 



The return of the Expedition, which took place very shortly after the 

 meeting of 1843, has closed this branch of our report in a manner the most 

 highly gratifying, whether we regard the magnitude and geographical interest 

 of its discoveries, the vast harvest of magnetic and meteorological obser- 

 vations it has secured, the extent of ocean traversed, and the consequent 

 importance of the data it has furnished towards the completion of the mag- 

 netic survey of the globe in its most difficult points; or, lastly, the triumph 

 of skill, conduct and perseverance on the part of the Commander of the Ex- 

 pedition, and every one concerned in it, which have under Providence been 

 the means of conducting so arduous and prolonged a struggle with every 

 material obstacle to a glorious and happy conclusion. 



The results of the magnetic observations made during the second year of 

 the operations of this Expedition Avill shortly appear under the form of a 

 ' Sixth series of Contributions to Terrestrial Magnetism,' by Colonel Sabine, 

 already printed for the Second Part of the Transactions of the Royal Society 

 for the current year. During this period, the ships, setting out from Hobart 

 Town and visiting Sydney and New Zealand in their progress, explored a 

 second time the great Icy Barrier in lat. 78° south, which had stopped them 

 in the former year, and which again resisted their efforts either to penetrate 

 it or to turn its eastern extremity. Quitting it at length and keeping nearly 

 on the 60th parallel of south latitude, they crossed the whole breadth of the 

 South Pacific to the Falkland Islands, where the observations of that season 

 terminate. Those of the last year of the Expedition not having yet been 

 placed in his hands, Colonel Sabine has forborne to anticipate the principal 

 part of the conclusions suggested by the materials thus brought under dis- 

 cussion, until supported by a complete and general review of their whole 

 mass. There are, however, some points of prominent interest which have 

 emerged from the discussion of the first two years' observations which ought 

 not to be passed over in silence. 



In the first place, Colonel Sabine considers it to have been rendered almost 

 certain, that in the two ships employed in the Expedition, and probably there- 

 fore in all ordinary sailing vessels, there is little or no appreciable amount of 

 permanent magnetic polarity (though in steamers or iron ships the ease may 

 be otherwise), but that the lohole of the transient polarity induced in the iron 

 by the earth's action at any given moment and locality is not instantaneously 

 destroyed and exchanged for a new magnetic state on a change of geogra- 

 phical place or angular position, though the greater part of it is so. A 

 residual polarity lingers as it were in the iron of the ship and fades out more 

 slowly, so that the vessel carries with it into every new point of its course 

 some trace and impress of the terrestrial magnetism of those which it has 

 left. This consideration, joined to the converse proposition, which it renders 

 exceedinglj^ probable (viz. that tlie magnetism which thus requires time for 

 its destruction is also not instantaneously developed), would render the pro- 

 blem of deducing rigorous results from observationa made during voyages a 



