THULEAN BASALTS 787 



The norms of these analyses are given in the Table VIII below. They 

 are alike in that albite and anorthite are present in almost equal amounts 

 in either, although the porphyritic lava shows much more of both than 

 does the -other. They differ notably, however, in that the Thorshavn 

 basalt shows no normative quartz, but, on the contrary, a little nephelite 

 and some olivine, while that of Waags-f jord is decidedly quaric, having 

 nearly 8 per cent of excess silica, and hypersthene instead of olivine. 

 These differences are expressed in the symbols given. Inasmuch as no 

 trace of nephelite is visible in the sections of the Thorshavn rock, it may 

 be supposed that the normative nephelite is represented modally by the 

 carnegieite molecule in the abundant feldspar, and it would be of interest 

 to separate and analyze the feldspar phenocrysts were sufficient material 

 available. 



Table VIII 



Norms of Faroe Basalts 



12 3 



Quartz 7.98 0.60 



Orthoclase 5.00 3.89 4.45 



Albite 27.77 18.34 25.15 



Anorthite 26.69 18.35 22.52 



Nephelite 2. 84 



Diopside 16.81 22.07 19.34 



Hypersthene 13.14 14.54 



Olivine 10.02 



Magnetite 4.41 4.41 4.41 



Ilmenite 5.17 9.12 7.30 



Apatite 1.01 1.01 1.01 



1. Thorshavn, Stromoe. (11)111.5.3.4(5). 



2. Waags-fjord, Suderoe. III. 4". 3(4) .4". 



3. Average, Faroe Islands. III. 5. 3". 4". 



OTHER THULEAN BASALTS 



Since I have been unable personally to study any Thulean basalts other 

 than those of Iceland and the Faroes, a few words must suffice for the 

 others, so that we may obtain a conspectus of the region. The more im- 

 portant references are given in each case. 



The plateau basalts of western Scotland, northern Ireland, the Heb- 

 rides, and Orkneys have been quite fully described in numerous papers 

 by Geikie, Judd, Teall, Harker, Peach and Home, Flett, and many other 

 British petrographers. 23 We may take the flows of Skye, well described 



23 See, for instance, Geikie : Ancient volcanoes of Great Britain, vol. ii, 1897 ; Harker : 

 Tertiary igneous rocks of, Skye, 1904 ; Flett : Trans. Roy. Soc. Edinburgh, vol. 39, 1900. 



