250 Dr. J. Kerr's Electro-optic 



by tension, and not affected by compression. The Ruhmkorff- 

 discharges gave afterwards an effect which was more purely 

 positive, weakened regularly by compression ; but the liquid 

 was now very much disturbed, and there was a large heat- 

 effect after a few discharges. 



Ethyl acetate acted hardly so well as the last. With mode- 

 rate charges of the jar, there was a large deformation of 

 the flame, and the regular effect was very faint, not seizable 

 indeed without the hand compensator ; but it was clearly 

 positive, strengthened by tension, and darkened by compres- 

 sion. 



Butyl acetate acted much better. As a conductor, without 

 the jar, it gave a clear effect which was purely positive by 

 both tests ; and with these feeble discharges the disturbance 

 of the flame was hardly noticed. 



Amyl acetate acted still better, but not without the jar. 

 With moderate charges it gave a good effect, which was 

 purely positive, strengthened by tension, and extinguished by 

 compression. With strong discharges the effect was still very 

 fine, and purely positive by both tests, the deformation of the 

 flame being hardly sensible. 



Butyrates, C 4 H 7 (C„H 2 „+i)0 2 . 



17. The regular effects in these compounds are purely po- 

 sitive and undisturbed, much stronger and finer than in 

 the acetates. 



Methyl butyrate acted well as a conductor, with or without 

 the jar, giving a series of fine effects with increasing charges, 

 and without any apparent disturbance. The effect, weak or 

 strong, was purely positive, extinguished always by the proper 

 compression parallel to lines of force. 



Ethyl butyrate, an impure sample, was hardly so strong 

 as the last, requiring the jar and five or more turns of the 

 plate. With good charges the effect was strong, and purely 

 positive by both tests. 



Ethyl isobutyrate was much stronger, acting well as a non- 

 conductor, and reminding me of the weaker hydrocarbons, 

 amylene &c. With strong charges of the jar it gave a strong, 

 slow, and very fine effect, purely positive by both tests, and 

 without sensible disturbance. 



Isobutyl isobutyrate gave a fine and purely positive effect 

 as a nonconductor. There was no sensible disturbance even 

 when the electric force was strongest. The action improved 

 evidently for a time as the experiment proceeded, and appeared 

 to be at last as strong as that of benzol. 



