1863.] 



451 



members of homologous series. Many such series were examined, 

 and the results are tabulated, the refractive index of A and the 

 length of the spectrum or dispersion being reduced, if necessary, 

 to 20 C., and the sensitiveness being taken for the 10 degrees rising 

 above 20 C. ; the specific refractive energy, dispersion, and sensitive- 

 ness also form part of the Tables. Methylic, ethylic, amylic, and 

 caprylic alcohols are the first series examined, and it is found that on 

 ascending the series the refraction increases ; the dispersion does so 

 still more rapidly, while the sensitiveness remains nearly the same. 

 Other homologous series of the same group, such as the iodides, 

 compound ethers, or mercury compounds, were also examined, and 

 they all agree in exhibiting a progressive change in refraction and 

 dispersion with the advancing members of the series ; but in which 

 direction and to what extent depend on the other substances with 

 which the compound radical is combined. Yet, if we regard not 

 the actual indices, but these, minus unity, divided by the density, a 

 pretty regular increase is found to take place as the series advance. 

 The following Tables exhibit this : 



Specific Refractive Energy. 



Specific Dispersion. 



