140 Royal Society. 



these stations it would he desirable, 1st, That regular hourly obser- 

 vations should be made (at least during the daytime) of the fluctua- 

 tions of the three elements of variation, dip, and intensity, or their 

 equivalents, with magnetometers on the more improved construction, 

 during a period of three years from their commencement. 



2ndly. That on days, and on a plan appointed, agreed on in 

 concert with one another, and with Eurojjean observatories, the 

 fluctuations of the same elements should be observed during twenty- 

 four successive hours, strictly simultaneous with one another, and at 

 intervals of not more than five minutes. 



3rdly. That the absolute values of the same elements shall be 

 determined at each station, in reference to the fluctuating values 

 above mentioned, with all possible care and precision, at several 

 epochs comprehended within the period allowed. 



4thly. That in the event of a naval expecHtion of magnetic dis- 

 covery l^eing despatched, observations be also instituted at each fixed 

 station, in correspondence with, and on a plan concerted with, the 

 Commander of such Expedition. 



As regards the second branch of the subject referred to them, 

 viz. the proposal of an Antarctic voyage of magnetic research, they 

 are of opinion, as already generally expressed, that such a voyage 

 would be, in the present state of the subject, productive of results 

 of the highest importance and value ; and they ground this opinion 

 on the following reasons : — 



1st. That great and notorious deficiencies exist in our knowledge 

 of the course of the variation lines generally, but especially in the 

 Antarctic seas, and that the true position of the southern magnetic 

 pole or poles can scarcely even be conjectured with any probability 

 from the data already known. 



2ndly. That our knowledge of the dip throughout those regions, 

 and the whole southern hemisphere, is even yet more defective, and 

 that even such observations of this element as could be procured at 

 sea, still more by landing on ice, &c., would have especial value. 



3rdly. That the intensity lines in those regions rest on observa- 

 tions far too few to justify any sure reliance on their courses over a 

 large part of their extent, and over the rest are altogether con- 

 jectural. Nevertheless that there is good reason to believe in the 

 existence and accessibility of two points of maximum intensity in 

 the southern as in the northern hemisphere, the attainment of which 

 would be highly interesting and important. 



4thly. That a correct knowledge of the courses of these lines, 

 especially where they approach their respective poles, is to be re- 

 garded as a first and, indeed, indispensable preliminary step to the 

 construction of a rigorous and complete theory of terrestrial mag- 

 netism. 



5thly. That during the progress of such an expedition, oppor- 

 tunities would of necessity occur (and should be expressly sought) 

 to observe the transitory fluctuations of the magnetic elements in 

 simultaneous conjunction with observations at the fixed stations and 

 in Europe, and so to furnish data for the investigation of these 



