TERRESTRIAL MAGNETISM. 315 



Page 239, in = 45°, log. a^^for 2*29724 read 2-29796. 

 — 251, in = - 13°, log. c^"^,for 1-27047 read 1-37047. 



The public is indebted to M. Weber for the map (PI. XVII.) 

 containing the values of the decHnation as computed from the Ele- 

 ments of the Theory of Terrestrial Magnetism (Scien. Mem. vol. 

 ii. page 211). In order to give a clearer view of the intricate form 

 of the system of lines of equal declination, the points at which the 

 dech nation has a maximum value, as well as those points where 

 two lines of equal declination intersect each other, (or where one 

 such line crosses itself,) have been computed with especial care. 

 There are two points of the first kind, and four of the second 

 kind. The common character of such points consists in this, 

 that the first differential of the declination in every direction 

 disappears. 



It is almost superfluous to remark, that in those regions 

 where the declinations alter very slowly on aU sides, as in 

 Southern and South-Eastern Asia, small alterations in the values 

 of the declination may produce very great changes in the form 

 of the system of lines. 



The same remark applies to the maps of the Total Intensity 

 (PI. XVIII. and XIX.) computed by Dr. Goldschmidt from the 

 tables, pages 236 — 251. 



These maps show, in the northern hemisphere, two points of 

 maximum intensity, and one point of intersection of lines of 

 equal intensity ; in the southern hemisphere, one point of maxi- 

 mum ; and in the middle zone, two points of minimum inten- 

 sity, and two points of intersection. 



Similar maps, grounded on the theory, are in preparation for 

 the inclination, for the horizontal intensity, for the three com- 

 ponents of the earth's magnetic force (i. e. the values of X, Y, 

 and Z), and for that distribution of the magnetic fluids on the 

 surface of the earth, which may be taken as the representative 

 of the actual distribution in the interior. We hope to publish 

 these maps in the Resultate for 1839. G. 



Note by the Translator. 



The maps of the Declination and of the Total Intensity, com- 

 puted according to M. Gauss's theory, are given in the present 

 number of the Scientific Memoirs. By the kind permission of 

 MM. Gauss and Weber, the translator is also enabled to give in 



Y 2 



