March, 1915. 



KNOWLEDGE. 



93 



From photographs h\ 



H.M. Geological Survey 



Figure 73. 



Figure 74. 



.\ photomicrogiaph of Luxulvanite, Luxulyan. X 30. .A photomicrograph of .Aiiorlhoclase-bearing Granite, 

 Ordinarv Light. Greadv Ouarrv. Luxulvan. X 14. X Nicols. 



Figure 7d. 



FUnt Implement found by Sir J. Prestwich at Downton, Wilts. 1869. 

 (Natural History Museum.) 



(From its Proceedings, by the courtesy of the Geologists' Association.) 



