76 NOTES TO BOOK XII. 



the effect of such observations as means of training men 

 in the pursuit of science. " There is amongst us," says 

 one of the magnetic observers, " a growing recognition 

 of the importance, both for science and for practical life, 

 of forming exact observers of nature. Hitherto astronomy 

 alone has afforded a very partial opportunity for the for- 

 mation of fine observers, of which few could avail them- 

 selves. Experience has shown that magnetic observations 

 may serve as excellent training schools in this respect." 

 Letter of W. Weber. Brit. Assoc. Rep. 1845, p. 17. 



Addition to Note (D). 



The function V, mentioned p. 73, is of constant 

 occurrence in investigations respecting attractions. It is 

 introduced by Laplace in his investigations respecting the 

 attractions of spheroids, Mec. Gel. Livr. in. Art. 4. Mr. 

 Green and Prof. MacCullagh have proposed to term this 

 function the Potential of the system ; but this term 

 (though suggested, I suppose, by analogy with the sub- 

 stantive Exponential,) does not appear convenient in its 

 form. On the other hand, the term Integral Proximity 

 does not indicate that which gives the function its peculiar 

 claim to distinction ; namely, that its differentials express 

 the power or attraction of the system. Perhaps Integral 

 Potentiality, or Integral Attractively, would be a term com- 

 bining the recommendations of both the others. 



