392 Intelligence and Miscellaneous Articles. 



As you have studied my paper so accurately, I was unwilling to 

 omit communicating to you the above, from which you will have 

 seen that in reality I am perfectly at one with you. 



I have since found some additional applications of this theorem 

 which I hope shortly to publish. Amongst others, Rose observes 

 (Pogg. Ann., vol. ciii. p. 311) that some minerals, for instance 

 Gadolinite, when heated to a certain temperature, begin suddenly to 

 glow in consequence of heat being set free. When they are heated 

 again, after being cooled, this glowing is not repeated. He discusses 

 the question whether this could be connected with a change of spe- 

 cific heat ; but evidently it is nothing but a transition from a state 

 of more to a state of less energy, Perhaps, however, we may con- 

 clude from this that this substance could not have been formed by 

 fire, at least not if it occurs in nature at the surface, but that it is 



rather of Neptunian origin. 



* * * * 



Yours, &c, 



H. W. Schroder v. d. Kolk. 

 To Professor G. C. Foster. 



The following are the additional errata indicated by Dr. Schroder 

 van der Kolk in his paper '* On the Velocity of Sound" (Phil. Mag. 

 S. 4. vol. xxx. p. 34, July 1865). 



Page 35, line 11 from bottom, for I was nevertheless convinced 

 read I was nevertheless not convinced. 



— 35, — 9 from bottom, dele not. 



— 38, — 8 from bottom, 



— 39, line 9 from bottom, 



for s= ; AlJl + 7(y±i)=_ 2 .^E\, 



read ,= . AH/3 f 1+ y(y+l)-j AVRH 



— 39, line 5 from bottom, 



for /K r . — Z. 



(2) 

 (2) 



