Scientific Intelligence. — Geology. 195 



olivin, 2.886. West wall of Longraw, Arthur Seat, 2.801. 

 Trap vein in the coal formation at CaroHne Park, near New- 

 haven, 2.764. Rock of the Gallon Hill, Edinburgh, 2.754. 

 Trap vein in clay-slate, Rothsay, Isle of Bute, 2.746. — Von 

 Dechen, 



9. Chemical Composition of some Secondary Rocks. — The 

 following analyses by two of our young friends will afford a 

 good general idea of the chemical nature of several rocks con- 

 nected with the coal formation near to Edinburgh. 



(1.) Analysis of Slate-clay , from Wardie, near Newhaven. 

 by Mr Robert Walker : It does not effervesce with acids, nei- 

 ther does it form a jelly with them. When exposed to a red 

 heat, it loses interstitial water, and splits into fragments. It is 

 found alternating with sandstone and bituminous shale of the 

 coal formation in the above mentioned neighbourhood. Its con- 

 stituents are. Silica, 60.00 ; alumina, 17.60; oxide of iron, 15.21 ; 

 lime, 2.36 ; loss by heat 4.41 : = 99,58. 



(2. ) Analysis of Compact Felspar from the Pentlands ; by Mr 

 John Drysdale. Specific gravity 2.53. Chemical characters: 

 Effervesces slightly, and does not gelatinize with acids. Before 

 the blowpipe, infusible per se. Heated on platinum-wire, with 

 an excess of the salt of phosphorus, it forms a transparent and 

 colourless glass. Constituent parts : Silica, 73.5 ; alumina, with 

 a trace of iron, 11.23 ; carbonate of lime, 2.5 ; potash, 3.55 ; 

 soda, 3.8 ; water, 4.6 : = 99.20. 



(3.) Analysis of Greenstone from Wardie, near Newhaven, 

 by Mr John Drysdale. — Effervesces, and does not gelatinize 

 with acids. Before the blowpipe, heated per se, it melts into a 

 black glass ; with the salt of phosphorus it melts into a trans- 

 parent glass, yellow when hot, and colourless when cold. Spe- 

 cific gravity 2.873. Constituent parts: — Silica, 44.00; alumi- 

 na, 11.4; iron (protoxide), 22.32; lime, 8.8; magnesia, 25; 

 water and carbonic acid, 10.5 : =: 99.52. 



(4.) Felspar Rock of Wardie, near Newhaven, by Mr Robert 

 Walker. — The following is the analysis of an ash-grey rock, 

 bearing a strong resemblance to compact Labrador felspar, 

 but differing materially in chemical composition. It is found 

 rising up among the strata of sandstone, slate-clay, and other 

 rocks of the coal formation, and indeed at first sight might be 

 taken for a Neptunian rock, were it not that it is distinctly seen 



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