354 Geology of 



These two specimens A and B, taken from the same lava-stream in 

 the tunnel, show by their analysis that they are more closely allied to 

 the dolerites than the trachytes, as, according to Bunsen, a normal 

 pyroxenic dolerite ought to have ouly 48.47 silica, whilst this lava 

 from the tunnel has 54.616, and has at the same time all the other 

 ingredients which constitute a normal dolerite in lesser proportion 

 than it ought to have. They are the two prevailing rocks occurring 

 near the northern end of the tunnel, and a comparison of their 

 analyses proves well, although so very different in their lithological 

 character, that they possess nearly the same constituents. 



Labradorite, large Feldspar Crystals occurring frequently embedded in 

 agglomeratic beds in BdnJcs 1 Peninsula. 



(J. Schapringer.) 



Per cent. 

 Silica ... ... ... 55.89 



Alumina 



Sesquioxvde of iron 



Lime 



Magnesia 



Soda 



Potash 



29-23 

 168 



12-43 

 0-65 

 0-69 

 0-24 



100-81 

 No loss by drying the specimen in the dessi.-ator. 



Analysis made by Professor A. W. Bickerton, F.C.S., at the Laboratory 



of Canterbury College. 



Vesicular Trachyte (Domite) from a Lava Stream, one mile east 



of Lyttelton. 

 Specific gravity ... ... 2 , 4A 



Adherent moisture 



Loss on ignition ... 



Silica and insoluble matter ... 



Alumina 



Iron 



Manganese 



Lime (Ca. O.) ... 



Magnesia 



Sulphuric Acid ... 



Potash 



Soda, loss and undetermined ... 



100-000 



1-000 



•900 



73170 



15-630 



2340 



trace 



1635 



•324 



-686 



3527 



•776 



