206 On the luminous Appearance of Sed Water. 



of silica. It had produced 0'5875 of a gramme of silica, and 

 had iherefbre taken up 0*2806 of a gramme of oxygen. This 

 experiment differs by about 2 percent, from the foregoing; 

 but both have tliis iaiih, that a portion of carbon is lost, as 

 a component part of the fuelid oil wherewith the water was 

 impregnated. 



5. Having seen the impossibility of obtaining a rigid re- 

 •ult by means of solutions of iron, [ undcruok to incor- 

 porate the base of silica with copper, bv n cans ot a similar 

 process of reduction with powder of ehurcoal. 1 he ?ili- 

 cated copper was dissolved in nitric acid, during which 

 there existed evident maiks of the presence of carbon, which 

 at first separated in tlie form of a brown powder; but 

 vanished, whilst the departing gas, conducted through lime 

 water, deposited a portion of carbonate of lime. The 

 copper dissolved to a clear fluid, which on cooling 

 thickened to a blue jelly, and left after drying and wash- 

 ing a gray siliceous earth, amounting to 5 per cent, of 

 the weight of the copper. Attempting to separate the 

 copper with so much nicety as to produce a more exact re- 

 sult than the preceding, circumstances occurred which 

 rendered a loss inevitable, and thereby made this experi- 

 ment still more uncertain. 



I have not tried to unite the base of silica with silver by 

 fusion with carbon, but I have no doubt of its success. 

 It will probably present a more accurate result, although , 

 the silver will also yield a sensible quantity of carbon 

 from its solutions in nitric acid*. As to the determination 

 of the precise quantities of oxycen and base forming silica, 

 I consider this as only of secondary importance; it is at pre- 

 sent sufficient, that these experiments determine with a to- 

 lerable certainty that silica, mixed with powder of charcoal, 

 can be reduced in fusion with a mielal, and that its base, 

 when the metal is dissolved in acids, is, by the absorption 

 of about an equal weight of oxygen, again converted into 

 silica. 



XXXVII. On the Luminous Appearance of Sea Water. By 

 Knight Spencer, Esq. 



To Mr. Tilloch. 

 Sir, J- HE luminous appearance which the sea (when 



• This experiment with silver has since been performed by the German 

 chemists ; and the result, as I have been informed, was tuch as Professor Ber- 

 2eliui hu here anticipated. — Edit. 



agitated) 



