A SODA-FELSPAR ROCK. 185 



specimens was 0-47 per cent. In Nos. 1 and 3, the bulk of the 

 iron and lime is in a form easily soluble in acids ; this is pretty 

 true of No. 2, but the soluble fraction is very small. 



J. J. Beringer. 

 No. I of foregoing analyses was the creamy grey variety, 

 with cavities filled with rusty material weathering out in 

 nodules beyond the white surface of the rock, contiguous 

 to the greenstone. 



No. II was a compact dark grey variety, weathering white, 

 from the summit of the Head, in close proximity to the 

 mass of slate. 

 No. Ill was the grey nodular spherulitic variety, weathering 

 grey, from the North-East corner of the Head. 

 Mr. J. Hort Player analysed a compact unweathered 

 specimen of the creamy grey variety of this rock, free from 

 nodules or cavities, and found the composition as follows : — ■ 



No. IV. 



Silica 666 



Titanic Acid '8 



Alumina 19'6 



Ferric Oxide ... ,., '9 



Ferrous Oxide .. ... "2 



Magnesia ... ... ... "3 



Lime ... ... ... "4 



Soda 9'8 



Potash '7 



Loss by ignition ... ... -8 



100-1 

 Mr. J. J. H. Teall, F.R.S., kindly examined microscopic 

 sections of the spherulitic rock forme, and reported as follows : — 



No. 353. A remarkable spherulitic rock, spherules sometimes 

 measuring :^-ineh in diameter. 



The central portions of the spherules are generally 

 composed of crypto-crystalline material. The outer por- 

 tions of radiating blades or prisms of felspar, presumably 

 albite. Ferric oxide, probably resulting from the 

 decomposition of a ferriferous carbonate, is scattered 

 through the slide in irregular patches, and concentrated , 

 in veins. Some of the patches, by their form, suggest 



