86 



TRANS. ST. LOUIS ACAD. SCIENCE. 



Final value, 52,6768 grammes. 

 z=: 812.93 grains. 



Left pan, 52.6770 grammes. 

 Right " 52.6769 " 



Mean 52.6769 " 



Left pan, 52.6785 " 



Right " 52.6750 " I 



V^'^'^ 52.6767 " 1 



Reduction to vacuum correction may be neglected ; I have, there- 

 fore, adopted the weight 812.93, presuming that the difference 

 between this value and that given by Mr. Schott is caused by 

 wear of the ring since it was weighed. 



Taking the co-efficient of expansion as o.ooooi' ^^ follows that 

 the moment of inertia k' ^oi the ring may be expressed by the 

 formula Ti', ~ 9.56562 + 0.000916 t, 



from which the following table has been constructed : 



The following determinations for the moment of inertia kt of 

 the magnet, at various temperatures, have been made, the reduc- 

 tions being obtained by means of the formula 



fit K t y,^2 y,2 



where k', z= moment of inertia of the ring, 



T r:= the time of oscillation of the magnet alone, 

 T' ^=. time of oscillation of the loaded magnet. 



Assuming log. ki =: log. /6,j -|- (i-'j^.'j) /\k. 



