310 Scientific Intelligence. [April, 



Article XIII. 

 SCIENTIFIC intelligknce; ani> notices of subjects 



CONNECTED WITH SCIENCE. 



I. Lectures, 



Mr. Singer will commence his Lectures on Natural Philosophy 

 on Monday, the 4th of April. A card of the arrangement may be 

 had at the lecture-room, 3. Princes-street, Cavendish-square j or 

 of Mr. Triphook, 37, St. James's-street. 



II. On New Properties of Light exhibited in the Optical 

 Pkeiiomena of Mot her-o/'- Pear l.^ 



T!ie splendid exhibition of colours which distinguishes mother-of- 

 pearl from every other body, and tlic successive developement of 

 fresh tints by every gentle inclination of the plate, do not arise, as 

 has always been supposed, from the lamellated structure of the 

 shell, but are owing to a new power of extraordinarij reflection, 

 and to a new faculty of separating the light into its component 

 parts. Both of these powers demonstrably reside without the sur- 

 face of the mother-of-pearl, and the light which produces the 

 brilliant colours has never penetrated the substance of the mother-of- 

 pearl. 



\Vhcn we look at the image of a candle reflected from a piece of 

 regularly formed niotber-oi-pearl ground upon a hone, but not 

 polished, we perceive on one side the common image, and at the 

 distance of 4 or 5°, an extraordinarily refected image highly 

 affected with the prismatic colours. The distance of this image 

 from the common image, or the angle of aberration, increases with 

 the angle of incidence, and the lines of the angles of aberration are 

 inversely as the lines of the angles of extraordinuiy reflection. By po- 

 lishing the mother-of-pearl a new image, exactly like the first, and 

 obedient to the same laws, is developed on the other side of the 

 common image. Two coloured images are also seen by transmission, 

 and the image which is faintest by reflection is always brightest by 

 transmission. 



The most remarkable circumstance, however, is, that the optical 

 properties, which have now been described, can be communicated by 

 pressure to wax, cements, gum arabic, balsam of Tola, realgar, tin 

 foil, the fusible metal made of bismuth and rnercury, and even to 

 lead by hard pressure, or by the blow of a hammer. All these 

 substances shine with the same brilliant colours as the mother-of- 

 pearl itself, and prove beyond all question that the colours are pror 

 duced by some particular configuration of surface, which is com- 

 municable Ic soft and fusible substances, and which cannot be 

 affected or removed by the finest polishing. 



* AVeare favoured with this and the following notice by Dr. Brewster. 



