On the Kinetic Theory of Gases. 95 



angles to the axes of the magnetic needles, and therefore the 

 needles are not in a position to have their magnetism much 

 altered by the passage of a current, unless that current 

 be very strong, the suspended magnet of the Rosenthal 

 galvanometer will tend to have its magnetism diminished 

 by every current sent through the instrument in such a 

 direction as to push the poles of the suspended magnet 

 out of the coil, since the lines of force of the two coils will pass 

 along the axis of the suspended magnet. Care not having been 

 taken to send the current round the Rosenthal galvanometer, 

 so as to always suck the ends of the magnet into the coils, is 

 probably the explanation of the weakening of its suspended 

 magnets during four years in the ratio of 5 to 1. Whereas 

 the falling-off in the sensibility of the first of the four gal- 

 vanometers in the preceding list in the ratio of 4*3 to 1 during 

 a shorter time is probably due to inferior steel having been 

 used in the construction of its magnetic needles. 



In view of the great difference which exists between various 

 specimens of magnet-steel, it is most important that only the 

 very best magnet-steel should be employed in the construction 

 of galvanometers which are intended to have a high sensibility, 

 since the factor of merit of the instrument depends largely on 

 the goodness of the magnetic needles. 



VII. Note on Boltzmann's Kinetic Theory of Gases, and on 

 Sir W. Thomson's Address to Section A, British Association, 

 1884. %E. P. Culverwell, M. A., Fellow of Trinity 

 College, Dublin*. 



BOLTZMANN has shown that, whatever be the law of force 

 between the particles of a gas, the configuration of the 

 gas will remain unchanged provided the number of particles 

 moving in a particular way be proportional to e~ hl , where I is 

 the total energy of a particle moving in that way. This may 

 be termed a permanent configuration. Mr. Watson has ex- 

 tended this to a system of molecules with any number of 

 degrees of freedom. 



But, so far as I know, no one has attempted to show that a 

 set of particles having any given initial conditions will, as 

 time goes on, approximate more and more to this permanent 

 configuration. Sir William Thomson indeed has stated (see 

 Montreal Presidential Address, Section A) that he believes it 

 " to be rigorously demonstrable that the whole translational 

 energy [of a perfectly elastic molecule] must ultimately 



* Communicated by the Author. 



