NOTES TO PRECEDING SECTION. 



121 



face of the earth, according to the observations hitherto col- 

 lected, appears to be 2;052, the minimum 0,706. Both phe- 

 nomena l)olongto the Southern hemisphere ; the first to 73° 

 47' S. lat., 169° 30' E. long., near Mount Crozier, West 

 North-West of the South magnetic pole, at a place where 

 Sir James Ross found the inclination of the needle 87° 11' 

 (Sabine, Contributions to Terrestrial Magnetism, 1843, No. 

 5, p. 231) ; the second, observed by Erman under 90° 59' S. 

 lat , 370 24' W. long., 80 miles eastward from the coast of 

 the province of Espiritu Santo, Brazil (Erman Phys. Beob. 

 1841, S. 570), at a point where the inclination is only 7° 55'. 

 The accurate relations of the intensity to one another are 

 therefore as I to 2-906. It was long believed that the great- 

 est intensity of the magnetic force was only two and a half 

 times as great as the weakest which the surface of our earth 

 manifests (Sabine, Report on Intensity, p. 82). 



131 (p. 57.) — On Amber (succinum, glessum) Pliny says, 

 xxxvii. 3, " Genera ejus plura. Attritu digitorum accepta 

 caloris anima trahunt in se paleas ac folia arida qu* levia 

 6unt, ac ut magnes lapis ferri ramenta quoque." (Plato, in 

 Timaeo, p. 80 ; Martin, Etudes sur le Timee, t. ii. p. 343— 

 346 ; Strabo, xv. p. 703, Casaub. ; Clemens Alex. Strom, 

 ii. p. 370, where, strangely enough, to aovxiov and to jjXe- 

 xpov are distins^uished.) When Thales, in Aristot. de ani- 

 ma 1, 2, and Hippias in Diog. Laertio 1, 24, attribute a soul 

 to the magnet and to amber, this animation only refers to a 

 moving principle. 



132 (p. 57.)_«« The magnet attracts iron in the same way 

 as amber attracts the smallest grains of mustard. It is like 

 a breath of wind which penetrates through both, and is com- 

 municated with the rapidity of an arrow." These words 

 are Kuopho's, a Chinese orator on the magnet, and writer ot 

 the beginning of the fourth century. (Klaproth, Lettre 4 

 M.A. de Humboldt, sur I'invention de la boussole, 1834, p. 

 125.) 



133 (p. 58.) — "The phenomena of periodical variations de- 

 pend manifestly on the action of solar heat, operating prob- 

 ably through the medium of thermoelectric currents induced 

 on the earth's surface. Beyond this rude guess, however, 

 nothing is as yet known of the physical cause. It is still a 

 matter of speculation, whether the solar influence be a prin- 

 cipal or only a subordinate cause in the phenomena of ter- 

 restrial magnetism." (Observ. to be made in the Antarctic 

 Exped. 1840, p. 35.) 



134 (p. 58.)— Barlow, in the Philos. Transact, for 1822, P. 

 i., p. 117; Sir David Brewster, Treatise on Magnetism, p. 

 129. Long before Gilbert and Hooke, it was taught in the 

 Chinese work. Ou-thsa-tsou, that heat lessened the direct- 

 ive property of the magnet. (Klaproth, Lettre d M. A. de 

 Humboldt, sur I'invention de la boussole, p. 96.) 



135 (p. 58.) — Vide the paper on Terrestrial Magnetism in 

 the Quart. Review, 1840, vol. Ixvi. p. 271—312. 



136 (p. 58.)— As the first demand for the establishment of 

 these observatories (a net-work of stations provided with 

 similar instruments) took its rise with me, I dare not cher- 

 ish the hope that I shall live long enough to see both hemi- 

 spheres covered in equal and due measure with magnetical 

 stations, under the control of able naturalists and astrono- 

 mers, and especially under the liberal and continued support 

 of the British and Russian governments. In the years 1806 

 and 1807 at Berlin, with my friend and fellow lal)ourer, 

 Oltmanns, particularly at the times of the solstices and equi- 

 noxes, I frequently observed the movements of the needle 

 from hour to hour, and even from half hour to half hour, 

 during five or six days and nights in succession. I had per- 

 suaded myself that continuous, uninterrupted observations 

 of several days and nights were preferable to the single ob- 

 servations of many months. The apparatus, a magnetic 

 telescope by Prony, suspended in a glass case from a thread 

 without torsi<m, enabled angles of 7 and 8 seconds to be 

 read off upon a finely-divided scale, fixed at a proper dis- 

 tance and illuminated at night with lamps. Magnetic per- 

 turbations (storms) which occasionally returned on several 

 successive nights at the same hours, led me even at that 

 time to desire most anxiously that similar apparatuses should 

 be used to the east and west of Berlin, for the sake of dis- 

 tinguishing general telluric phenomena from those of a lo- 

 cal nature, and that may depend on perturbations in the un- 

 equally-heated body of the earth, or in the cloud-forming 

 atmosphere. My removal to Paris, and the lengthened po- 

 litical disturbances which spread over the whole of the west 

 of Europe, prevented my wish from being accomplished at 

 this time. The light diffused by the great discovery of Or- 

 «ted (1820), of the intimate connection between electricity 

 and magnetism, finally aroused the general interest after its 

 long sleep, in the periodical change of the electro-magnetic 

 charge of the earth. Arago, who many years before had 

 begun the longest unbroken series of hourly observations 

 which we possess in Europe in the observatory of Paris, 

 with an admirable declination instrument by Gambey, show- 

 ed, by means of simultaneous observations of perturbation 

 made at Kasan, what advantages resulted from correspond- 

 ing measurements of variation. When I returned to Berlin, 

 lifter a residence of eighteen years in France, I had a small 



magnetic house erected in the autumn of 1628, not only with 

 a view to carrying out the work begun in 1806, but especial- 

 ly that simultaneous observations, at hours previously agreed 

 upon, might bo made at Berlin, Paris, and Freiburg (at a 

 depth of 35 fathoms under the surface). The simultaneous- 

 ness of the perturbations, and the parallelism of the move- 

 ments for October and December, 1829, were there graphi- 

 cally represented (Poggend. Annal. Bd. xix. S. 357, Tab. 

 I. — III.). An expedition into the North of Russia, underta- 

 ken in 1829 by command of the Emperor, gave me an oppor- 

 tunity of extending my plan upon a great scale. This plan 

 was unfolded to a committee especially named in one of the 

 imperial academies of science ; and under the protection of 

 the chief of the mining corps. Count von Cancrin, and the 

 excellent superintendence of Prof. Kupffer, magnetic sta- 

 tions were fixed over the whole of the north of Asia, from 

 Nicolajeff by Catherinenburg, Barnaul, and Vertschinsk, to 

 Peking. 



The year 1832 (vide Cutting, gelehr. Anzeig. St. 206) 

 marks the great epoch in which the profound author of a new 

 theory of terrestrial magnetism, Frederick Gauss, erected 

 apparatus, constructed upon new principles, in the Gottin- 

 gen Observatory. In 1834 the magnetic observatory was 

 finished, and in the same year Gauss spread his instruments 

 and his n^ethod of conducting observations, in which the 

 distinguished natural philosopher, William Weber, took 

 great interest, over a large portion of Germany, Sweden, 

 and Italy (Resultate der Beob. des magnetischen Vereins 

 im Jahr. 1638, S. 135, and Poggend. Annalen, Bd. xxxiii. 

 S. 426). In the magnetical association that was now form- 

 ed, with Goftingen f^or its centre, at four periods of the year, 

 ever since 1836, hourly observations for an entire day were 

 regularly instituted, but which were not those of the equi- 

 noxes and solstices which I had proposed and followed in 

 1830. Up to this lime. Great Britain, in possession of the 

 largest commerce in the world, and with her wide-spread 

 navy, had taken no part in the movement, which, since 1828, 

 had begun to afford important results towards the determi- 

 nation of terrestrial magnetism. I was so fortunate, in a 

 public appeal from Berlin to the Duke of Sussex, then Pres- 

 ident of the Royal Society, by my letter of April 1836, head- 

 ed, " Lettre de M. de Humboldt A S. A. R. le Due de Sus- 

 sex sur les moyens propres a perfeclionner la connaissance 

 du magn6tisme terrestre par I'^tablissement de stations 

 magn^tiques et d'observations correspondantes," to excite a 

 lively interest in the undertaking which had so long been 

 the object of my warmest wishes. In my letter to the Duke 

 of Sussex I urged the erection of permanent stations in Can- 

 ada, St. Helena, the Cape of Good Hope, the Isle of France, 

 Ceylon, and New Holland, all of which I had, however, 

 pointed out as advantageous positions five years previously. 

 There was a joint physical and meteorological committee 

 appointed in the Royal Society, which, besides fixed mag- 

 netic observatories in both hemispheres, proposed to the 

 government to fit out a naval expedition for magnetic obser- 

 vations in the Antarctic Seas. I need not here proclaim all 

 that science owes in this conjuncture to the zeal and activity 

 of Sir John Herschel, Col. Sabine, Professor Airy, and Mr. 

 Lloyd, as well as the powerful support that was given by 

 the British Association for the Advancement of Science as- 

 sembled at Newcastle in 1838. In June, 1839, the Antarc- 

 tic expedition, under the command of Captain James Clarke 

 Ross, was resolved on ; and now, since its fortunate return, 

 we enjoy the double fruits of important geographical discov- 

 eries in the neighbourhood of the South Pole, and a series of 

 simultaneous observations in eight or ten new magnetic sta- 

 tions. 



137 (p. 58.) — Instead of ascribing the internal heat of the 

 earth to the transition of matter from a state of gaseous fluid- 

 ity to the solid condition on the formation of the planets. Am- 

 pere has broached what to me appears a very improbable 

 opinion, viz., that it might be a consequence of an incessant 

 chemical action of a central mass of earth and alkali-metals 

 upon the external crust undergoing oxydation. " On ne peut 

 douter," he says, in his masterly Theorie des ph6nomenes 

 61ectro-dynamiques (1826, p. 199), " qu'il existe dans l'int6- 

 rieur du globe des courants electro-magnetiques, et que ces 

 courants sont la cause de la chaleur qui lui est jiropre. lis 

 naissent d'un noyau metallique central compos6des mfetaux 

 que Sir Humphrey Davy nous a fait connaltre, agissant sur 

 la couche oxid6e qui entoure le noyau." 



138 (p. 58.) — The remarkable connection between the 

 curvature of magnetic lines and (hat of my isothermal lines 

 was first observed by Sir David Brewster (Transactions of 

 the Royal Society of Edinburgh, vol. ix. 1821, p. 318, and 

 Treatise on Magnetism, 1837, p. 42, 44, 47, and 268). This 

 distinguished natural philosopher admits two " poles of 

 maximum cold" in the northern hemisphere ; one American 

 (730 N. Lat., 102° W. Long., near Cape Walter) ; another 

 Asiatic (73° N. lat., 78° E. Long.) ; whence, according to 

 him, arise two hot and two cold meridians, t. e. meridians 

 of greatest heat and greatest cold. In the 16th century, 

 however, Acosta (Hist. nat. de las Indias, 1589, lib. i. cap. 

 17), resting what he says on the observatioj^s of a highly 



