184 Scientific Intelligence — Mineralogy. 



smalts in many industrial purposes; but as it is not an enamel 

 colour, its employment is not applicable in the colouring of china 

 and earthenware. — Pharmaceutical Journal and Transactions, vol. 

 xi., No. v., p. 230. 



MINERALOGY. 



7. Exhibition of Statues and Gems in the Crystal Palace. — The 

 nature of the articles exhibited depends as much upon the character 

 of the building which is to receive them as it does upon their own 

 individual character. In a building which admits the whole light of 

 the sky, except where it is eclipsed by the beams of its carpentry, it 

 would be impossible to make a favourable exhibition of pictures, 

 while statues could be advantageously displayed. When an oil 

 painting is illuminated from numerous points, or by broad beams of 

 light, the varnished surface, thus rendered visible, destroys the JBnest 

 touches of the artist, and removes the illusion which he had produced. 

 In like manner, gems, such as the diamond, which derive their prin- 

 cipal beauty from the prismatic spectra which they produce, lose all 

 their charm when exhibited in a palace of crystal, while gems and 

 precious stones, which derive all their beauty from their colour, are 

 displayed to great advantage. The great Koh-i-noor, or Mountain 

 of Light, the Durra-i-noor, or the Sea of Light, and the fine blue 

 diamond of Mr Hope, have less effect, as now exhibited by day- 

 light, than a piece of glass of the same size and tint would have, 

 if exhibited in a private room with two or three windows. In the 

 spectra produced by broad luminous spaces, all the colours are re- 

 combined into white light, and hence the disappointment which every 

 person has experienced at the first sight of these singular gems. 

 Were the same gems to be worn by a lady in a drawing-room, with 

 numerous bright lights, their effect would astonish the company.* 

 The fine coloured refractions of the diamond disappear also under 

 other circumstances. When the diamonds are very small, and set 

 closely together, the numerous prismatic spectra which they produce 

 are mingled, and produce white light on the retina of the eye, and 

 this diminution of colour increases with the number of lights. When 

 small diamonds, however, are at a sufficient distance from each other, 

 they are seen to the greatest advantage when the lights are sharp 

 and numerous. 



As the sight of rare precious stones must always be exceedingly 

 interesting, because they are never seen in collections of minerals, 

 and when in the possession of individuals can only be seen by their 

 private friends, it would have been desirable to place all the diamonds 

 (»s the Koh-i-noor is, on Fridays and Saturdays), in a dark apart- 

 ment, illuminated by numerous small and brilliant lights. Till this 



* Many intelligent persons mistook the hollow foil for the great diamond 

 itself. 



