V3 =S9, 



94- On the Refractive and Dispersive Power of Chloroform. 



The numbers in the last column should vary as the cubes 

 of those in the first, or be as 1, 8, 27. It we deduct 10 grains 

 from each of them for the action of the weight of the wire 

 depressing it, we shall have these numbers — 



90 710 2390; 



dividing respectively by 1, 8, and 27, — 



90 89 88-5. 



Hence the mean result for Mf — j , for D = '25, or — = y^^, 



is nearly 89 grains, consequently, 



M 

 (100)^ 

 and M = 89,000,000 grains. 



But a foot in length of the wire in question weighs 1 1 grains. 

 The equivalent modulus of elasticity is therefore very nearly 

 8,000,000 feet of the wire in question, which agrees closely 

 with the received numbers for steel wire. 



2. Note respecting the Refractive and Dispersive Poisoer of 

 Chloroform. 



From an experiment made in very cloudy weather, and 

 therefore rather unfavourable light, I determined the following 

 indices of refraction for pure chloroform, prepared by Dr. 

 George Wilson, ofsp. gr. 1*4966. 



The measure of the refracting angle of the prism was 39° 

 ■tl'. References were made to the principal lines of the spec- 

 trum, as below : the temperature of the fluid was probably 54-°. 



Extreme red j«,= l'44'75 



B (in the red) . 1*4488 



D (in the orange-yellow) 1*451 



b (in the green) 1*456 



F (in the blue) 1*457 



H (in the violet, being the least refran-"! 1.4,63 



gible of the two groups so designated) J^ 



Extreme violet 1*4675 



Hence the refractive index is by no means remarkably great, 

 being nearly that of wax, spermaceti, and several of the essen- 

 tial oils. 



The dispersive power, or — ^j is equal to '045, which again 



agrees nearly with that of the essential oils. The high specific 

 gravity of the body appears to have no marked influence in 

 increasing its action on light. 



