Intelligence and Miscellaneous Articles. 327 



a second sphere : — d = 59*85 millim. ; s = 8*9 ; X = 474974.-1 912 * 

 These numbers for X agree sufficiently well with those found for 

 copper wires, as follows: — Jacobi, X = o74i ifl.-i Qp "> Kirchhoff, 



X = ' 451043-10" ; W - Weber ' X= 463382-10"' Eor g^anoplastic 



1 

 copper X= 5X3144^015- 



I have the honour to be, Gentlemen, 



Tour most obedient servant, 

 Freiburg i. B., March 1884. *■ Himstedt, Dr., Professor. 



To the Editors of the Philosojphiccd Magazine and Journal. 



Gentlemen, 

 1 regret that I was unacquainted with Dr. Himstedt's papers 

 when preparing my communication referred to in the above. The 

 first paper I have not at present access to ; and I did not find 

 it mentioned by any subsequent writer on the subject. On refer- 

 ring to the second paper, I find, in addition to the very interesting 

 experimental verification, a discussion of the general solution for 

 solid spheres. This latter, however, is of a much more analytical 

 character than the investigation contained in my paper, in which 

 one of my aims was to reduce the mathematical analysis to as nar- 

 row limits as possible, replacing it by a discussion of the physical 

 phenomena. A comparison of the results shows agreement when 

 a slip in my work is corrected. On page 17 the expression for G 

 at the top of the page should be (see also Errata) 



H$» 



d(j) 



and each expression for a couple on pages 17, 18, 19 should be 

 multiplied by a. This requires that the value of P 2 at the foot 

 of page 19 should be divided by a; and in the special case con- 

 sidered makes F=93 nearly, or about 200 times the Earth's mag- 

 netic force. Indeed the dimensions will not otherwise be correct. 



I remain, Gentlemen, 



Tours obediently, 

 Queen's College, Galway, J. Laemor. 



March 22, 1884. 



Errata. 



Page 11, line 7, for iiric read ±ira 2 n 



— 11, — 23, for density read thermal capacity 



— 14, — 10, for (? - «)* read (|- *) / s 



— 17, — o, for d$ read dp 



