166 Dr. J. Kerr's Electro-optic 



with five turns of the plate, strong with ten turns ; and the 

 effect was purely negative. 



Cinnyl alcohol, C 9 H 9 HO, is purely negative. Tried in the 

 fusion-cell at a temperature a little above its melting-point, 

 33° O.j it acted well as a conductor. With ten turns of the 

 plate it gave a clear and pretty strong effect, which was found 

 to be purely negative by both tests. 



Glycol, (C 2 H 4 )" H 2 0*2, is very feebly and impurely negative. 

 This is a very inconvenient liquid to work with, viscous and 

 heterogeneous, giving permanent deformations of the flame, 

 and impure initial extinction in the polariscope. With strong- 

 est charges of the jar, it gave a mere trace of effect, which 

 appeared to be negative. With the strongest Ruhmkorff-dis- 

 charges, the restorations were clearer, and almost perfectly 

 regular, but still faint, and obscured by disturbance. The effect 

 was pretty surely negative, strengthened sensibly by compres- 

 sion parallel to lines of force, but not extinguished by tension. 



Glycerin, (C 3 ~H- 5 y u H 3 3 , is certainly, but feebly and im- 

 purely, negative. As far as I can judge from my samples, 

 this liquid is more unsuitable even than glycol for delicate 

 optical work. With the Ruhmkorff's coil, it acted better than 

 glycol, giving very good retorations, notwithstanding great 

 disturbance produced hj the syrupy structure of the plate. 

 The effect was found to be certainly negative, though the 

 neutralizing action of tension was not always seized. 



Phenol, C 6 H 5 HO, is purely positive. In the fusion-cell, 

 at or above 35° C, it acted well with the plate machine and 

 without the jar, but required several turns of the plate. There 

 was generally some optical disturbance by heterogeneous 

 structure, and also by movements in the liquid, when the elec- 

 tric force was intense ; butthe optical effect was regular and 

 very distinct, purely positive by both tests. 



Oleic acid, C 18 H 34 2 , is purely and strongly positive. Tried 

 in the plate cell as a non-conductor, it acted more intensely 

 than any of the fatty acids — gave a regular and pretty strong 

 effect, which was strengthened by tension parallel to lines of 

 force, and extinguished perfectly by compression. 



Lactic acid, C 3 H 6 3 , is apparently positive. Tried with 

 strongest charges of the jar, and afterwards with the coil, it 

 gave a regular effect, undoubtedly pure, and pretty surely 

 positive, but too faint and abrupt to be characterized with 

 perfect certainty. The liquid was evidently a very weak in- 

 sulator. 



Oxides, (C»H 2n+1 ) 2 0. 



9. The only two of these that have been examined are purely 

 negative, and much stronger than the corresponding alcohols. 



