Chemistry and Phj/sics. 2G9 



I is carefully passed over the surface to be silvered, and when this applica- 



I tion is dry it is removed by another plug of cotton, and the plate ob- 



tained perfectly clean. The glass is then laid on the table, a portion of 

 the silvering fluid poured on to the surface, and this spread carefully over 

 every part by a cylinder of india-rubber stretched upon wood which has 

 previously been cleaned and wetted with the solution; in this manner a 

 perfect wetting of the surface is obtained, and all air bubbles, &c, are 

 removed. Then more fluid is poured on the glass until it is covered 

 with a layer about the ^th of an inch in depth, which easily stands upon 

 It ; and in that state its temperature is allowed to rise. In about ten 

 minutes or more, silver begins to deposit on the glass, and in fifteen or 

 twenty minutes a uniform opaque coat, having a greyish tint on the upper 

 surface, is deposited. After a certain time the glass employed in the 

 « illustration was pushed to the edge of the table, was tilted that the fluid 



I might be poured off, was washed with water, and then was examined. 



The under surface presented a perfectly brilliant metallic plate of high 

 reflective power, as high as any that silver can attain to ; and the coat of 

 silver, though thin, was so strong as to sustain handling, and so firm as 

 to bear polishing on the back to any degree, by rubbing with the hand 

 and polishing powder. The usual course in practice, however, is, whe 



I 



1 



i 



the first stratum of fluid is exhausted, to remove it, and apply a layer of 

 No. 2 solution ; and when that has been removed and the glass washed 

 and dried, to cover the back surface with a protective coat of black var- 

 nish. When the foim of the glass varies, simple expedients are employed ; 

 and by their means either concave or convex, or corrugated surfaces are 

 silvered, and bottles and vases are coated internally. It is easy to mend 

 an injury in the silvering of a plate, and two or three cases of repair were 

 performed on the table. 



The proposed advantages of the process are, — the production of a per- 

 fect reflecting surface ; the ability to repair ; the mercantile economy of 

 the process (the silver in a square yard of surface is worth l^, %d,) ; the 

 certainty, simplicity, and quickness of the operation ; and, above all, the 

 dismissal of the use of mercury. In theory the principles of tlie process 

 justify the expectations, and in practice nothing as yet has occurred which 

 is counter to them. 



6. Some observations on divided gold ; by Prof. Farad A v, D.CX., 

 F.R.S. (ib,, p. 310).— With regard to the second part of the evening's 

 discourse, the speaker said he had been led by certain considerations to 

 seeK experimentally for some efiect on the rays of light, by bodies which 

 when in small quantities had strong peculiar action upon it, and which 

 also could be divided into plates and particles so thin and minute as to 

 come far within the dimensions of an undulation of light, whilst they 

 still retained more or less of the power they had in mass; and though 

 he had as yet obtained but little new information, he considered it his 

 <l^ty, in some degree, to report progress to the members of the Royal In- 

 stitution. The vibrations of light are, for the violet ray 59,570 in an 

 inch, and for the red ray 37,640 in an inch; it is the lateral portion of 

 "the vibration of the ether* which is by hypothesis supix>ssed to affect the 



# 



or other fluids, 

 V 336, Aa 



may easily be obt^ed on the surface of watei 

 bed in the Philosophical Transactions for 1831 



