232 



the light of the electric spark of high tension continues for less than 

 the millionth part of a second, and it has been shewn that the bright- 

 ness of the impression, produced by light on the eye, increases in 

 the exact arithmetical proportion of the time during which it con- 

 tinues to act on the retina, it follows that the apparent brightness of 

 the electric spark is only tooVo o ^^ what it would become if the 

 duration of the spark could be prolonged to xV^h of a second. From 

 the great apparent brilliancy of the nearly instantaneous electric 

 spark of high tension, when compared with the sensibly continuous 

 light of Voltaic electricity, it is inferred that the brightness of elec- 

 trical light increases with the tension of the electricity. 



3. Note on the Refractive and Dispersive Powers of the Hu- 

 mours of the Eye, detei'mined by Experiment. By John 

 Adie, Esq. 



The author's object in undertaking these experiments, was to dis- 

 cover if the achromatism of the eye could be accounted for by the 

 differences in the dispersive ratios of the fluids forming that organ. 



The indices for several of the fixed lines were determined in the 

 aqueous humour ; with the crystalline no satisfactory result could be 

 obtained. 



In subjecting the vitreous humour to experiment, only the strongest 

 of the fixed lines could be seen, and that with great difficulty ; one 

 remarkable feature, however, was observed, viz., that on dividing the 

 mass of humours two spectrums were formed, the one placed over the 

 other, having a greater deviation, and, consequently, refractive power. 

 Thus proving, that that humour is not of equal density throughout, 

 as has heretofore been supposed. 



The following Donations to the Library were announced : — ■ 



The London University Calendar for 1849. 8vo. — Bi/ the Uni- 

 versity. 



The Ethnological Journal, No. 10. 8vo. — By the Editor. 



Suite of the Collection of Hydrographic Charts, with Sailing Direc- 

 tions, &c. — By the Lords Commissioners of the Admiralty. 



