

467 



arrangements to be made in carrying out their proposals, if 

 adopted. 



There is another point to which your Committee consider their 

 attention ought to be paid simultaneously with the establishment of 

 the proposed observatories : it is that of the extension of Magnetic 

 Surveys of the districts in their immediate neighbourhood, with a 

 view to fixing the situation and direction of the iso-magnetic curves 

 within some considerable adjoining area (in the case of the Falkland 

 Isles that of the whole group). 



On this point the following remarks by General Sabine, in a com- 

 munication addressed by him to us in reply to certain inquiries which 

 we considered it right to make of him, are in the opinion of your 

 Committee, conclusive in deciding them to recommend that provision 

 be also made for the execution of such surveys, collaterally with the 

 observations at the fixed stations. 



" Recent observations in North America, discussed in the ' Proceed- 

 ings of the Royal Society' for January 7th, 1858, have made known 

 that the general movement of translation of the isoclinal and isogonic 

 lines, which from the earliest observations have been progressing from 

 west to east, has within a few years reached its extreme eastern 

 oscillation, and that the movement in the reverse direction has already 

 commenced ; we live therefore at an epoch in the history of terres- 

 trial magnetism, which we have reason to believe will be regarded 

 hereafter when theory shall have more advanced as a highly im- 

 portant and critical epoch. The geographical position of the maxi- 

 mum force in the Northern Hemisphere appears to have reached its 

 extreme easterly elongation, and from this time forth may be expected 

 to move for many years to come towards the meridian which it occu- 

 pied in Halley's time, accompanied by a corresponding change in the 

 positions and forms of the isodynamic, isoclinal, and isogonic lines 

 in North America : a careful determination of the absolute values 

 and present secular change of the three elements at this critical theo- 

 retical epoch, at stations situated on either side of the American con- 

 tinent, and nearly in the geographical latitude of the maximum of 

 the force, would furnish therefore data for posterity, of the value of 

 which we may have a very inadequate appreciation at present. I 

 may refer to the discussion prefixed to the third volume of the To- 

 ronto Observations, to show that the means and methods with which 



