

459 



In the first place, the mean state of the several magnetic elements 

 for each of the stations, as reduced to a fixed epoch, has been obtained 

 with a precision of which nothing previously done has afforded any 

 example emulating, in this respect, the exactness of astronomical 

 determinations, and competent to serve as a fixed point of departure 

 to the latest ages ; and this for each of the elements in question 

 the dip, the declination, and the intensity of the magnetic force. 



Secondly, that at each station, the rate of regularly progressive 

 secular change in all the three elements above mentioned has been 

 ascertained with a degree of precision which contrasts strongly with 

 the loose and inaccurate determinations of former times. 



Thirdly, that the laws of the diurnal, annual, and other periodic 

 fluctuations in the values of these elements, as exhibited at each sta- 

 tion, have been established in a manner and with a decision to which 

 nothing hitherto executed in any branch of science, astronomy ex- 

 cepted, is comparable ; and that the results embodied in the exa- 

 mination of these laws have laid open a view of magnetic action so 

 singular, and so utterly unexpected, as to amount to the creation of 

 a new department of science, and the detection of a completely novel 

 system of physical relations : for that, in the first place, the systems 

 of diurnal and annual magnetic changes have each been separated 

 into two perfectly distinct and physically independent systems, the 

 one, at any particular station, holding its course according to laws 

 depending solely on the sun's hour-angle at the moment of observa- 

 tion, and his meridian altitude at different seasons, the other, com- 

 prehending all those movements which, under the name of magnetic 

 storms, or " irregular disturbances," have hitherto presented the 

 perplexing aspect of phenomena purely casual, capricious in amount 

 and in the particular occasions of their occurrence when regarded 

 singly, has been shown, by these discussions, to be subject in its 

 totality to laws equally definite with the others, though more depend- 

 ent for their application on peculiarities of local situation. As regards 

 the first of these systems of fluctuation, they find it demonstrated : 



That the sun's regular action on the magnetism of the globe is 

 determined by a law of no small complexity and intricacy, but which, 

 nevertheless, has been traced with precision and certainty, and shown 

 to be referable, in the first place, and for one of its arbitrary coeffi- 

 cients, to the geographical situation of the place of observation with 



