388 Chemical Analyses of' Rocks, 



Lime, 6 A ; Soda, 4.45; Water and Carbonic Acid, 3.3; =99.65. 

 The above analysis by Mr J. Drysdale, affords another inte- 

 resting example of the chemical change induced in neptunian 

 rocks by plutonean agency. 



II. 



1. Analysis of the Basaltic Rock of Largo Law in Fifeshire. 



The beautiful hill named Largo Law, which rises 938 feet 

 above the level of the sea, is composed of a greyish-black com- 

 pact basaltic rock, belonging to the greenstone or dolerite se- 

 ries. It rises through the surrounding rocks of the coal-forma- 

 tion, in which it has occasioned changes of position, structure, 

 and probably also in composition. The rock, although gene- 

 rally massive, in some parts of the hill appears disposed in ele- 

 gant columns. As it had not been analyzed, I put a specimen 

 of it into the hands of Mr J. Drysdale, who returned the fol- 

 lowing account of his examination of it : 



Specific gravity %Jdl\. Chemical Characters : It neither ef- 

 fervesces nor gelatinizes with acids. Before the blowpipe per se, 

 it melts easily into a black mass ; with the salt of phosphorus 

 into a transparent and colourless glass ; with borax ditto, &c. 

 Constituent Parts : Silica, 45.2; Alumina, 14.4 ; Protoxide of 

 Iron, 14.0; Lime, 12.7; Magnesia, 6.55 ; Soda, 5.22; Water, 

 2.4; = 100.47. 



2. Analysis of the Zeolite named Wollastonitey by Thomson, 



Fine specimens of this mineral were found in the greenstone 

 cliffs of Corstorphine Hill, by one of our best geological ob- 

 servers. General Lord Greenock. The following is Mr Wal- 

 ker's analysis of the Wollastonite from this new locality : It 

 phosphoresces when heated, giving out a feeble white light. It 

 does not effervesce nor afford a perfect jelly with acids. Heated 

 per se before the blowpipe, it fuses with effervescence into a 

 very hard white enamel. Its constituents are : Silica, 54.00 ; 

 Lime, 30.79; Soda, 5.55 \ Water, 5.43; Magnesia, 2.59; Alu- 

 mina and Oxide of Iron, 1.18; =99.54 



