144 REPORT— 1844.* 



very difficult one, were it not that the portion of magnetic power which thus 

 lingers in the iron is extremely small compared with that which obeys the 

 laws of soft iron in its instantaneous generation and destruction. 



Another conclusion of a very general and positive character respects the 

 forms of the magnetic lines in the southern hemisphere, especially those of 

 declination. From the assemblage and projection of all the observations of 

 this element, Colonel Sabine is led to the conclusion that the system of mag- 

 netic ovals in the southern hemisphere is really a double one, completelj' 

 analogous to that which prevails in the northern ; so that the two hemispheres 

 do actually possess, with respect to each other, a converse or complementary 

 character indicative of a certain symmetry in the disposal of the magnetic 

 forces or in the action of their causes. 



The situation of the Isogonic lines of the South Pacific at the present epoch, 

 as deduced from these observations, and brought into comparison with the 

 best evidence we possess of the situation of corresponding parts of the same 

 lines, or which comes to the same thing, of lines cutting several of them con- 

 tinuously at right angles, fully corroborates and bears out another general 

 proposition, viz. that the march of the magnetic phsenomena in this region of 

 the globe is steady, rapid, and in a westerly directio7i. 



In projecting the lines of equal intensity deduced from the Antarctic ob- 

 servations, Colonel Sabine has been led to compare them with those theore- 

 tically deduced by the numerical interpretation of Gauss's formulae. The 

 most important distinction between M. Gauss's isodynamic and those result- 

 ing from observation is, that Gauss's are nearly circular curves round a single 

 centre, whereas those of observation appear to be two distinct systems of 

 curves. In the northern hemisphere the two systems are separated; in the 

 southern, tiie progress of secular change appears to have brought them to 

 run into each other, producing, by the conjunction of two ovals, one very 

 lengthened oval, in which however the trace of the double curvature is still 

 recognizable. The two foci in the south appear to have nearly the same 

 values as those in the north. 



British Colonial Magnetical and Meteorological Observatories. 



The volume of the observations made at the observatory at Toronto in 

 Canada, from its commencement to the end of 1S42, has been for some time 

 in the press, and will be distributed at home and abroad in the course of the 

 winter. The volumes containing the observations at Van Diemen's Island, 

 the Cape of Good Hope and St. Helena to the same period, are in a very 

 forward state of preparation, and will be printed and circulated with no other 

 delay than such as may arise in the printing and engraving such voluminous 

 works. The volume for Toronto will include the comparison of the simul- 

 taneous observations made in the group of stations on the North American 

 continent. The Van Diemen Island volume will compare the observations 

 at Hobarton with those of the Antarctic Expedition at many points of the 

 southern hemisphere, the two together representing the magnetic phaenomena 

 which occurred over a considerable portion of that hemisphere, on tlie pre- 

 scribed days and instants when the observers in Europe, Asia and America 

 were recording, each at his own station. Witii St. Helena and the Cape of 

 Good Hope will be grouped the obser%'ations made on the same system and 

 with the same instruments by the French observers at Algiers, which have 

 been supplied for that purpose by the kind intervention of M. Arago. Cadiz, 

 from whence observations are also expected, ranks also with this group, which 

 may be viewed as representing the portion of our western hemisphere inter- 

 mediate between the Falkland Islands and Cape Horn (where the Antarctic 



