Atmosphere and the Earth. 257 



those of equal intensity. But if, by degrees, differences in the 

 surface temperature arise, it is clear that the lines of equal inten- 

 sity in particular will change, and will remove in some points from 

 those of equal inclination. If a line of equal inclination passes 

 through several points, which have the same terrestrial tempera- 

 ture, then, in all these points, the intensity of the magnetic force 

 will also be the same ; but in all points of the same line, where 

 the terrestrial temperature is higher or lower, will the intensity be 

 greater or less (if the second hypothesis be correct). This ap- 

 pears really to be the case ; and if future observations increase 

 the number of those ah'eady collected, we may consider this cir- 

 cumstance as a powerful confirmation of the second hypothesis. 

 From Hansteen's chart (of the lines of" inclination and isody- 

 namic lines for the whole magnetic power for 1825, also from 

 the chart of isodynamic lines, which is appended to his^Treatise 

 in Poggendorf's Annals, v. 9.), we see that the inclination and 

 isodynamic lines in Scotland run nearly parallel ; but in the east, 

 in Norway and Sweden, the latter deviate to the north, and in- 

 tersect the former : On the line of equal inclination, therefore, 

 in the east, the intensity is less than in the west, which is also 

 the case with the terrestrial temperature. Edinburgh has nearly 

 the same inclination as Stockholm ; in Edinburgh the intensity 

 is 1-400, the terrestrial temperature 47-75 ; in Stockholm, the 

 first 1-386, the other 43-7. The same is the case with Paris and 

 Kasan, whose inclinations differ little from one another ; in Paris 

 the intensity is 1348, the terrestrial temperature 527 ; in Ka- 

 san, the former 1320, the latter 43-25. Further, in Teneriffe 

 and Naples : in Teneriffe the intensity = ] -298, terrestrial 

 temperature 64-62 ; in Naples, the former 1275, the latter 

 about 61-25. 



We now easily see why the pole of intensity falls to the soyth 

 of the pole of inclination. As the temperature of the earth de- 

 creases to the north, so the lines of equal inclination lying near- 

 est the pole of inclination, go to the north of it throuoh colder 

 points than to tiie south ; but in these colder points, from tlie 

 above principles, the intensity must be less than in the warmer ; 

 we must therefore seek for the pole of intensities, viz. the point 

 where the intensities reach their maximum, to the south of the 



JANUAKV .MARCH 1830. Jt 



