EXPLANATION OF THE PLATES 



PLATE I 



Figure 1. — Microphotograph of rock 438 x 11 diameters (about). 



Figure 2. — Microphotograph of rock E. 36 x 19 diameters. The colourless holo- 

 crystalline base consists of acid felspar intergrown with sodalite. The small, sharply 

 defined, dark prisms are wohlerite, bright orange in colour. 



Figure 3. — The same x 55 diameters. Owing to the non-actinic colour of the larger 

 wohlerite crystals they have photographed black. The difference in refractive 

 index between the felspar and sodalite is indicated by the " Becke's effect." 



Figure 4. — Microphotograph of rock 443 x 11 diameters. The photograph contains 

 more than the normal proportion of biotite. 



Figure 5. — Microphotograph of rock 372 x 18 diameters. The dark prisms are horn- 

 blende. 



Figure 6. — Microphotograph of rock 7 x 55 diameters, showing the fine-grained 

 panidiomorphic mixture of hornblende, biotite, and felspar. 



PLATE II 



Figure 1. — Microphotograph of rock E. 11 x 19 diameters, showing the general aspect 

 of the rock with strongly corroded hornblende and corundum grains. 



Figure 2. — The same x 55 diameters, showing sharply idiomorphic phenocrysts of 

 anorthoclase. 



Figure 3. — Microphotograph of rock 452 x 11 diameters. 



Figure 4. — The same x 62 diameters, showing the character of the composite horn- 

 blende crystals. 



Figure 5. — Microphotograph of rock 440 x 31 diameters, showing well-defined tremolite. 



Figure 6. — Microphotograph of rock 1278 x 55 diameters. 



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