406 Intelligence and Miscellaneous Articles. 



was found to be reduced in the part corresponding to that which had 

 been exposed to light, but there was no reduction in that part which 

 had been preserved from light. Certain fine specimens of porcelain 

 acquire this activity more easily. 



A steel plate polished at one part, and roughened at another by 

 the action of aquafortis, and well cleaned by alcohol, was exposed to 

 the sun for two or three hours under the following conditions — half 

 the polished and unpolished plate under an opake screen, and the 

 other half under a white glass. The plate was then covered by a paper 

 prepared with albuminized chloride of silver. After twenty-four 

 hours' contact, an impression was formed on the unpolished part which 

 had been exposed to the light, but none on the polished part, nor on 

 -the unpolished part under the screen. A roughened glass plate 

 carefully cleaned gave similar results. 



These experiments show that it is not necessary for the reduction 

 of silver salts that there be a chemical action, as when a metallic 

 salt is insolated with an organic matter. M. Arnaudon has repeated 

 some of these experiments with different gases, and has obtained the 

 same results as with air. 



I may here recall a previous observation, that the insolated earth 

 exhibits traces of this action to a depth of a metre, the thickness 

 varying, of course, with the nature of the soil and the degree of in- 

 solation. The following experiment supports this view : — In a tin 

 tube lined with pasteboard impregnated with tartaric acid, and in- 

 solated so as strongly to reduce silver salts, I placed in the middle of 

 the tube, but not in contact, a small bladder containing a weak so- 

 lution of starch ; after forty-eight hours this starch feebly reduced 

 Barreswil's liquor, while other starch placed in the same conditions, 

 excepting the insolation, produced no effect on the liquor. 



The following experiments were made with a view of trying 

 whether light could magnetize a steel bar, as has frequently been 

 stated. Avoiding all sources of error, a knitting-needle suspended 

 by a hair was entirely unattracted by another needle insolated for a 

 very long time in a beam of light concentrated by a strong lens, 

 whether the light was white or had traversed a violet glass. 



I then enclosed a needle in a paper impregnated with nitrate of 

 uranium, or tartaric acid, and insolated ; I also suspended a needle 

 horizontally in tubes containing insolated pasteboard ; and the results 

 were always negative, as also was the case with experiments made 

 with very feebly magnetized needles in the hope of demagnetizing 

 them. 



In conclusion, this persistent activity imparted by light to porous 

 bodies cannot be the same as phosphorescence ; for, from Becquerel's 

 experiments, it would not continue so long : it is probable that, as 

 Foucault believes, it is a radiation invisible to our eyes, and which 

 does not traverse glass. — Comptes Rendus, July 1, 1861. 



ON TERRESTRIAL REFRACTION. BY M. BABINET. 



A ray of light which traverses the layers of the atmosphere 

 horizontally, is deflected from its rectilinear path towards the earth 



