114 ANNUAL OF SCIENTIFIC DISCO VEIIY. 



to this is a strong yellowish orange, then two emerald green colors 

 nearly touching ; after these, and at some distance off, is a rich ultra- 

 marine blue, and lastly a yiolet. So far relates to color; but the rays 

 evolved from the luminous mercury do not end here. Beyond the 

 violet is another intensely energetic ray, but which, to be rendered 

 apparent to the limited range of the eye, must be received upon some 

 fluorescent screen, such as a piece of paper washed over with a solu- 

 tion of sulphate of quinine, or allowed to fall on a sensitive collodion 

 plate. This latter surface makes known to us some other interesting 

 properties of this light. Not only will this invisible ray impress itself' 

 strongly upon the plate, but the last two visible colors, viz., the rich 

 ultramarine blue and the violet, are also seen to rival it in photo- 

 graphic action. Beyond these are other rays, equally energetic in 

 their actinic power, and mounting higher and higher into the almost 

 unknown regions of this invisible and mysterious part of the spectrum. 

 The mercurial electric light thus appears to be almost unique in its 

 properties, since, unlike other artificial lights, it is pre-eminently dis- 

 tinguished by the intensity and number of its photographic rays. Its 

 peculiar properties will, however, obviously prevent its coming into 

 general use at present. Tims, let any one imagine an assembly being 

 illuminated with a light which is deficient in ninety-four per cent, of 

 those colored rays which are usually met with in sunlight. Only 

 those colors would be visible which were capable of reflecting the 

 identical ray of the spectrum contained in the mercury light, and 

 everything else, of whatever color it might be by daylight, would be 

 totally black. Instead of having a thousand varied hues and tints to 

 rest the eye upon, we should be limited to the six colors named 

 above, and their combinations; and any one who has considered for 

 a moment how intimately any system of internal illumination depends 

 for its success upon the facility of reflecting and showing up varieties 

 of colors and tints, will at once see that a source of light, however 

 brilliant and valuable, could scarcely meet with private or public 

 approbation if it were so signally deficient in discrimination as to 

 transform the warm glow of health on a fair girl's cheek to the 

 ghastly and cadaverous hue of death. 



APPLICATION OF ELECTEICITY TO THE EXPLOSION OF GUN- 

 POWDER. 



The following is an abstract of a recent lecture on the above sub- 

 ject, delivered before the London Chemical Society, by Professor 

 Abel, Director of the Chemical Establishment of the War Department 

 (English): 



The lecturer commenced by giving a short historical account of 

 the experiments instituted in this and foreign countries for the pur- 

 pose of firing mines and cannon by electric agency, and referred to 

 particular methods of operation adopted by Colonel Verdu, in Spain, 

 and by M. Savare, in Paris, and to very extensive operations carried 

 on by a system organized by M. du Moncel, at the port of Cherbourg- 

 by MM. Dussaud and Rabattu, in 1854. The Austrian system of 

 employing frictional electricity, and results of great magnitude ob- 

 tained with it, were also briefly referred to. 



