Improvements in Science. 1 1 ' 



sequence. Neither does roughness appear to he a determin- 

 ing quality, for, though generally, the smooth surfaces are 

 lower on the list, this is not universal. The rough sul- 

 phate of barytes is lower on the list than the smooth car- 

 bonate of lead. Plumbago occupies a low place, and Indian 

 ink a comparatively high one. The best radiators do not 

 appear to belong to any particular class of bodies ; litmus 

 paper and Prussian blue are next each other, while sul- 

 phuret of lead, and bi-sulphuret of tin are separated by 

 an interval of 15 bodies. We have no doubt, that this 

 subject will attract more attention in this country, as it 

 is fraught with considerable practical utility. 



4. Effect of Light in magnetizing Needles.— Mr. Draper* has 

 repeated the experiment of Mrs. Somerville, which consisted 

 in rendering a needle magnetic by placing it under a piece 

 of glass, or blue ribbon, having half its length protected by 

 paper. He did not succeed. He made a very delicate ex- 

 periment, by admitting " a divergent beam of light through 

 a hole in the shutter of a dark room ; the cone of luminous 

 matter, at its apex, was about ^th of an inch in diameter, 

 and a hair, or other filament held in it, exhibited the phe- 

 nomena of diffraction ; the colours being received into the 

 eye by a lens. Across this beam a silver wire was adjusted, 

 and each of its extremities connected with cups of mercury, 

 which communicated with the poles of a voltaic battery. It 

 was expected that, if there was any action between a mag- 

 netic filament and light, some derangement would be seen 

 in the diffracted fringes, when the current passed ; but 

 none such was observable." He found also, that solar light 

 concentrated upon a delicate needle, produced no effect, 

 either in the air or in vacuum. " A needle made of watch 

 spring, about 4 inches long, which in an exhausted receiver, 

 suspended by a filament of silk, exhibited no polarity, had 

 one half of it exposed to the violet ray, cast by an equi- 

 angular prism of flint glass. This ray was separated from 

 the others, by passing it through a slit in a metallic screen, 

 and half the needle shielded by a piece of paper. After two 

 hours exposure, it was suspended again in the exhausted 

 receiver, but still showed no token of polarity; it was then 

 exposed to the other rays successively, with the same result." 

 * Journal of the Franklin [natitute, February, ikj.'i. 



