Phosphorescence and Colour by Electricity. 281 



the position of the particles, that when heat is ultimately 

 applied, the vibrations produced are fewer and comparatively 

 weaker. 



Note. Since my previous communication, I have been 

 informed of a work devoted to phosphorescence, and also of 

 an article in Gmelin's Chemistry, both in the German lan- 

 guage*. On referring to the abstract contained in parts of 

 the latter work, it appears that electricity has been employed 

 with phosphori ; and that certain bodies, phosphorescent by 

 heat, whose property had been destroyed by calcination, had 

 the property restored by electric shocks : any doubt upon the 

 subject might perhaps be decided by consulting the original 

 authority. My attention has also been called to some experi- 

 ments by Mr. Skrimshire (Encycl. Metrop., Art. Electricity, 

 . 177), in which transient phosphorescence was conferred upon 

 different substances by drawing sparks from them, or passing 

 electrical discharges over them. The eyes were kept closed 

 until the sound of the discharge was heard, and the light then 

 observed. I am not acquainted with the detail of these 

 experiments, and my own train of investigation was conducted 

 independent of them, and was nearly concluded before I be- 

 came aware of any similar inquiry. 



ON THE DARKNESS BETWEEN THE PRIMARY AND 

 SECONDARY RAINBOWS. 



BY MR. AINGER. 

 [In a Letter to M. FARADAY, Esq., F.R.S., &c.] 



MY DEAR SIR, 10, Doughty-street, Oct. 1830. 



TN consequence of your remark a few days since, that you 

 had not seen a satisfactory explanation of the darkness 

 between the primary and secondary rainbows, I have referred 

 to several of the most accessible works on the subject, and I 

 find that the phenomena of the rainbow are in general very 

 imperfectly, and in many cases very incorrectly, described. I 

 do not discover that the darkness in question, though suffi- 

 ciently obvious, is ever alluded to ; nor does it appear to me 



* Placidus Heinrich, Phosphorescenz derKorper, vol. iv. Gmeliu's Handbuch 

 der Chemie, part i. 



