442 On the Experimental Relations of Gold to Light. [1857. 



to a ray of light passing through it. When fine gold-leaf was 

 on the glass and inclined to the ray, it polarized the light, and 

 exactly in the same manner and direction as a bundle of glass 

 plates in the same position in the air. More light passed than 

 when the gold-leaf was in air, but it could not be so completely 

 polarized ; the minimum light was of a pale bluish colour. A 

 thinned gold-leaf produced the same effect, but let more com- 

 mon light through. I think the difference between gold-leaf and 

 sulphide of carbon is sensibly less than that between the 

 metal and air. The depositions of deflagrated gold, the films of 

 gold obtained by phosphorus, and even the heated deflagrated 

 gold, produced polarizing effects, which, though not large, 

 were easily recognized and distinguished from the non-action 

 of the glass. Gold-leaf and gold films on glass produced a 

 like effect in a camphine-bath, the results being easily di- 

 stinguished from those of the glass and camphine only, in 

 places where the glass had been cleared from gold. 



Films of palladium, rhodium, silver, a plate with deposited 

 gold particles, and a layer of deflagrated silver particles gave 

 a like result, the effect varying in degree. The sulphuret of 

 copper before spoken of as in contrast with the metals, gave 

 only doubtful result, if any. 



Before concluding, I may briefly describe the following 

 negative results with the preparations of gold. I prepared a 

 powerful electro-magnet, sent a polarized ray across the mag- 

 netic field, parallel to the magnetic axis, and then placed por- 

 tions of the ruby and violet fluids, also of their deposits wet 

 and dry, also portions of the gold films, of gold-leaf, the results 

 of deflagrations, &c., in the course of the ray ; but on exciting 

 the magnet, could not obtain any effect beyond that due to the 

 water or glass, which in any case accompanied the substance 

 into the magnetic field. In some cases very dense preparations 

 of the ruby and blue deposits were employed, the intense 

 electric lamplight being required to penetrate them. 



I passed the coloured rays of the solar beam through the 

 various gold fluids and films that have been described. For 

 this purpose a beam of sunlight entering a dark room through an 

 aperture ^th of an inch in width, was sent through two of Bon- 

 temps's flint-glass prisms, and its rays were either separated, or 

 at once thrown on to a pure white screen ; the different objects 



