CHAP. VII., 8.] ELECTRICITY (MAGNETISM). GENERAL SABINE SIR J. C. ROSS. 



197 



(907.) O fl the whole, it is no small praise to say that the 

 Great great geometer of Gottingen occupies the same rank 

 merit of j n ^ e theoretical science of terrestrial magnetism as 

 Kepler did in the theory of astronomy. That a per- 

 son devoted for the greater part of his life to pursuits 

 connected with the most abstract geometry, should 

 have at last thrown himself with so much zeal into 

 the practical solution of a complicated experimental 

 problem, is a circumstance as rare as it is praise- 

 worthy. Gauss lived long enough to see his methods 

 adopted all over the world, and his name honoured 

 His death, amongst every civilized people. Gauss died at Got- 

 tingen (where he had resided since 1807), in great 

 tranquillity, on the 23d February 1855, in the 78th 

 year of his age. 



But to obtain the data of the empirical theory with 

 exactness, it is evident that expeditions fitted out ex- 

 pressly with accurate apparatus, and directed at once 

 to many points of the habitable globe, are indispen- 

 sable. Powerful governments can alone effect this ; 

 and to Baron Humboldt is due (as has been shown) 

 the praise of having vigorously pressed the import- 

 ance of these upon the governments of England and 

 of Russia. The vast marine resources of the former, 

 and the peculiar magnetic interest of the stupendous 

 Asiatic territory of the latter, rendered their co- 

 operation highly important. In the result, Great 

 Britain has accomplished by far the larger share of 

 this vast enterprise. 



To Major-General EDWARD SABINE, of the Royal 

 Artillery, is mainly due the judicious management of 

 these magnetic explorations, and the speedy and skilful 

 publication of their interesting results. During the 

 course of an active life he has enjoyed opportunities 

 of making extensive observations with magnetic ap- 

 paratus and with the pendulum (238) throughout a 

 great range of latitude. His experiments (carried on 

 principally between the years 1819 and 1826) were 

 made in Brazil, the coast of Guinea, Spitzbergen, and 

 Arctic America. His observations on magnetic inten- 

 sity are particularly valuable, and first indicated the 

 position of a region of maximum intensity in North 

 America considerably to the south of the magnetic 

 pole as indicated by the dipping needle. To him 

 we also owe a valuable Intensity Chart of the Globe, 

 and a Magnetic Survey of the British Islands, pub- 

 lished in the reports of the British Association for 

 1836 and the two following years. 



But his efforts in promoting and directing the 

 system of national magnetical research set on foot at 

 Baron Humboldt's instigation are of still greater 

 importance, to which, in its earlier stages, the exer- 

 tions of Dr Lloyd (550) were also of essential service. 

 Although seconded by young, able, and enthusiastic 

 officers of the service to which General Sabine be- 



(910.) 

 British 

 magnetical 

 expedi- 

 tions. 



longs, the difficulty of starting simultaneously sys- 

 tematic observations (with instruments new and little 

 understood, and dispersed to the widest possible ex- 

 tent over the surface of the globe), was evidently very 

 great. Canada, St Helena, the Cape of Good Hope, 

 and Van Diemen's Land, were selected for primary 

 stations ; and the vastly voluminous results of hourly 

 or two-hourly observations of numerous instruments 

 continued year by year came pouring in to the central 

 establishment at Woolwich under General Sabine's 

 presidency. Besides these, several nautical expedi- 

 tions were fitted out for similar purposes, the most 

 important of which was sent in 1840 under the direc- 

 tion of Sir James Clark Ross to approach as nearly Captain 

 as might be to the Antarctic Pole. This voyage, whe- ir J> c * 

 ther in respect of the spirit of adventure displayed, 

 the wonderful character of the natural objects re- 

 vealed by it for the first time to human view, or the 

 importance of the scientific results obtained, may 

 rank with any of our memorable polar expeditions. 

 By the aid of an ingenious instrument contrived by 

 Mr Fox, trustworthy magnetical observations were 

 made on dip and intensity (as well as on declina- 

 tion) even in the open sea, and thus the area contri- 

 buting to our knowledge of the earth's magnetism 

 was vastly increased. The results of these researches 

 properly reduced have been gradually laid before the 

 world by General Sabine in a series of memoirs of 

 the utmost interest, contained in the Philosophical 

 Transactions from 1840 to the present time. 



With regard to the geographical phenomena of (911.) 

 magnetism, it may now be inferred almost with cer- Geogra- 

 tainty that the position of the Antarctic magnetic pole ^^^ 

 is in a region hitherto inaccessible, and to the south curves O f 

 of New Holland, placed somewhere near longitude intensity. 

 150 E., and probably not within 17 of the pole of 

 the earth, a latitude which was reached by Sir James 

 Ross in a longitude somewhat farther east. 1 It ap- 

 pears also that in the southern as in the northern 

 hemisphere there are two centres of greatest intensity, 

 round which the curves of equal intensity form ovals, 

 and afterwards loops like lemniscates. The stronger 

 magnetic centres of each hemisphere are near, though 

 apparently not coincident with, the two proper mag- 

 netic poles. The following numbers approximately re- 

 present on a scale of absolute intensity (898), in which 

 the grain, the foot, and the second are units, the 

 magnetic force at the four centres just mentioned ; 

 the second column contains the corresponding values 

 on Baron Humboldt's scale, mentioned in Art. 885. 



Absolute. 

 In North America, . . . 14'2 



In Siberia, 13'3 



South from New Holland, . 15-14 

 The other Antarctic centre, 14-9 



On Hnmboldt's Scale. 

 1-88 

 1-76 

 2-00 

 1-97 



The absolute intensity at St Helena, which is not far 



See General Sabine's Charts in Phil. Trans., 1844. 



