Scientific Intelligence. 155 



ib; CEderi Canada ; Patteseens Carlton-house ; Capillar is Rocky- 

 mountains ; Limusa Hudson's Bay ; Pseudo-cyj)ervs Cumberland- 

 house; Filiformis Cumberland-house; Amputtacea Bear Lake. — 

 (Silliman's American Journal, xxviii. 270.) 



IV. — Royal Institution.— 22nd January. 



On Silicified Fossils. — Dr. Faraday began his observations on 

 the conversion of ancient woods into siliceous matter, by detailing the 

 characters of silica, its insolubility in acids when in a dry pulverulent 

 state, and its ready solubility in water when fused with an alkali, 

 alluding, in passing, to the method which we possess by means of 

 fluor spar of obtaining it in an elastic, gaseous form. Whether it can 

 be sublimed by the direct agency of heat seems doubtful. Dr. 

 McCulloch relates an experiment in which he exposed silica to a 

 strong heat in a crucible, and apparently sublimed a portion. It is 

 possible, however, that in this instance there might have been some 

 fallacy. Dr. Faraday exhibited specimens of flint, from the chalk, 

 agates which may be considered a kind of siliceous nodules occurring 

 in trap rocks, and a beautiful example of cap rock crystal to illustrate 

 the deposition of the siliceous matter in layers. He shewed also a 

 fine amethyst containing colourless layers on its surface, which were 

 thicker on some places than on others, and gave it as his conclusion 

 drawn from an inspection of all the different forms of silica, that it 

 had been deposited by one law, because we find agates, chalcedony, 

 rock crystal, and other forms, united in the same mass. The for- 

 mation of chalcedony, he considers, cannot be accounted for by the 

 mere drying of gelatinous silica, the contraction which would follow 

 being too great to correspond with the forms in which we find chal- 

 cedony. 



Silicified woods are found lying on the surface of siliceous and cal- 

 careous formations, as in Africa and Antigua. In some specimens 

 we find that the soft parts of the wood yield first, and are replaced 

 by silica, while in others, we observe the hard parts giving way and 

 the soft parts remaining. In others again, both hard and soft por- 

 tions have disappeared, and have been entirely replaced by silica. Spe- 

 cimens from Antigua exhibit trees silicified in all stages of decay. In 

 one specimen which the lecturer shewed, the exterior circles were 

 silicified, and exhibited the vessels of the plant in perfect preserva- 

 tion, while the centre had been hollow and was filled up with agate. 

 There is no evidence to prove that silicification has taken place in mo- 

 dern times. The effect produced by the Geyzers is merely incrusta- 

 tion, for the substances upon which the silica from these springs is 

 deposited remain entire ; silicification, however, consists in the dis- 

 placement of organic matter by silica. Several instances ,haye been 

 related of the effect of rivers in silicifying or petrifying with silica, as 

 of the waters of the Aar, Danube, and Loch Ncagh ; but the loca- 

 lities to which this power was assigned, when examined by competent 

 authorities exhibited no such property. Specimens of what have 

 been considered by some as silicified sugar canes were shewn by Dr. 



