Cuap. VIL., § 8.] 
Baron ology and Magnetism than upon any others which he 
a cultivated. His conception of Isothermal Lines and 
Meteoro- his treatment of the subject of Climatology in his re- 
logy—tIso- markable paper of 18171! gave a new impulse to the 
' thermal former subject. His magnetical observations in his 
Lines. —_ voyage to the Equator have already been adverted to. 
Magnetism. Besides this we are indebted to Baron Humboldt for 
directing attention to the simultaneous and seemingly 
1 ~ accidental disturbances of the magnetic needle which 
take place over vast portions of the area of the globe. 
He commenced observations on this subject in con- 
junction with M. Oltmanns as early as 1806; and 
. during his residence in Paris he no doubt encouraged 
his friend Arago in those elaborate observations on 
the hourly variations of the needle which, to the 
irreparable loss of science, remained unpublished 
whilst they might have been most useful.?- In 1829 
simultaneous observations were made in Germany 
and Russia, and compared by MM. de Humboldt, 
Dove, and others, with interesting results.? It is 
probable that the results then obtained instigated 
Gauss to the enlarged enquiry to which I shall imme- 
diately refer. M.de Humboldt had already addressed 
the Russian Government on the same subject, sug- 
gesting the registration of hourly observations in their 
vast territories; and these, the first systematic ob- 
servations of the kind, have been continued ever 
since. The suggestion of ‘Term Days” of continuous 
registration of the Declination Needle was also due 
to Baron Humboldt. In 1836 he addressed the 
President of the Royal Society of London on the same 
subject, and his letter formed the basis of the exten- 
sive undertakings which have formed the contribu- 
tion of the British Government to this great enquiry. 
Baron Humboldt still lives at Berlin, enjoying the 
respect of all who know him, and the distinguished 
fayour of his Sovereign. 
(895.) 
Cart Friepricu Gauss, late Professor of Astro- 
nomy at Géttingen, belonged to that group of cele- 
brated geometers who illustrated the commencement 
of this century, and of which he was for some years 
the last survivor; but he too has now passed 
away. 
Gauss was born at Brunswick on the 30th April 
Daas on 1777, of humble parents, and was indebted for a 
mathema- liberal education to the notice which his talents pro- 
ticalworks. cured him from the reigning duke. His earliest 
original researches were in the theory of numbers. 
His Disquisitiones Arithmetice were published in 
1801, and were as profound and original as they 
have always been considered obscure even by those 
devoted to such studies. Gauss demonstrated the 
possibility of geometrically inscribing a regular poly- 
96. 
Nei 
(897. 
His may 
ELECTRICITY (MAGNETISM).—BARON HUMBOLDT—GAUSS. 
993 
gon of 17 sides within a circle; the only extension 
of geometry in this direction since the time of Euclid. 
His Theoria Motiis Corporum Celestium, published 
in 1809, is a very remarkable treatise on the geome- 
trical theory of the planetary orbits; in which it 
was shown for the first time how the elliptic ele- 
ments of a heavenly body may be deduced from 
three observations only of longitude and latitude,— 
an important extension of Newton’s eelebrated de- 
monstration in the case of parabolic cometary orbits. 
In the same work the method of least squares 
(85) was fully unfolded in its applications to astro- 
nomy. 
These and many other important labours all con- 898.) 
nected with the higher mathematics, had obtained Researches 
for Gauss an exalted place among the men of science pare pha 
of his time, long before he commenced those re- netism. 
searches on Terrestrial Magnetism, in virtue of 
which his name is introduced into the present sec- 
tion. It can hardly be doubted, however, that by 
these—scarcely begun before he had entered on his 
55th year—he will be hereafter chiefly remembered. 
His first work on the theory of magnetism* was pub- 
lished in 18338, and excited very general notice, as it 
contained a remarkable application of the Theory of 
Attractions to the distribution of magnetism in a 
steel bar, a singularly ingenious and rigorous proof 
of the primary law of the magnetic force, and like- 
wise a new and practical application of a suggestion Magnetic 
thrown out by Poisson, of amethod by which the foree in 
magnetic directive force of the earth itself may be jiescure. 
expressed in absolute measure, irrespectively of the 
constancy of the magnetism in the bar which is in 
the first instance used to estimate it. For this purpose 
two kinds of observation are required,—1st, By vibrat- 
ing a needle or bar of known weight and dimensions, 
and observing the time of its oscillation, the force 
pulling it into the meridian is ascertained in terms 
of the ordinary dynamical units. The time depends 
jointly on the magnetic force of the earth, and on 
that of the bar, or it varies inversely as the product 
of the two. 2dly, Another bar, B, is suspended like 
the first, A, in the magnetic meridian. A is then 
brought to act upon B, so as to draw it permanently 
out of the meridian. The position in which B rests 
determines the ratio of the magnetic force of the 
earth and of the bar A. But quantities whose pro- 
duct and whose ratio are given in known measures, are 
also known; whence the separate intensities of the 
earth’s and the bar’s magnetism may be eliminated.° 
Having thus fairly entered on a career of mag- 
netic experiments, Gauss proceeded, in conjunction ead 
with an experienced physicist of Gdttingen, Professor truments, 
Wilhelm Weber (420), to invent new apparatus for 
(899.) 
1 Memoires d’Arceuil, tom. iii., p. 462. 
8 See abstract in Bibliotheque Universelle, Aoit 1832. 
2 Posthumously published in his Quvres. 
* Intensitas vis magnetice terrestris ad am ab 
ta. Gott. 1833, 
6 The wnit of force to which these intensities are referred is that force (in grains) which acting on unit of mass through unit 
of time (a second) generates in it unit of velocity (a foot). 
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