330 Reports and Proceedings — Geological Society of London. 



The Totternhoe Stone is traced through Norfolk, but is thin at 

 Hunstanton (2 feet) ; its existence, however, enables the limits of 

 the Chalk Marl to be defined, with the result that some 13 feet of 

 the hard Chalk at Hunstanton must be referred to that subdivision. 



The Grey Chalk also thins northward, and from 90 feet near 

 Cambridge, is reduced to about 30 at Hunstanton. The Belemnite- 

 marls are traceable in Norfolk, but either thin out or are replaced 

 by hard white chalk near Heacham. 



The Melbourn Eock is continuous, and maintains similar charac- 

 ters throughout. 



The total diminution in the thickness of Lower Chalk is from 170 

 feet at Newmarket to 55 feet at Hunstanton, viz. 115 feet. An 

 endeavour was made to estimate the amount and extent of Ganlt 

 removed by erosion from Arlesey and Stoke Ferry. 



3. " On some Occurrences of Piedmontite-schist in Japan." By 

 B. Koto, Esq. Communicated by Frank Eutley, Esq., F.Gr.S. 



The occurrence of mangan-epidote or piedmontite in connexion 

 with the glaucophane-bearing rocks, in the crystalline schists of 

 Japan, had already been indicated by the author. But the " mura- 

 saki " or violet-rock contains it as an essential component. This 

 is well developed near Tokusima, and its geological range has been 

 traced further. The piedmontite occurs in this rock along with fine 

 quartz-grains under a schistose arrangement, the accessories being 

 muscovite, greenish-yellow garnet, rutile, some felspars, iron- 

 glance, etc. 



The crystals of piedmontite are elongated, cracked, and much 

 striated, and occur with the orthopinacoid parallel to the planes of 

 schistosity. The crystal faces are, as a rule, well developed, thus 

 differing from common epidote, regarded as a rock-forming mineral. 

 Twinning is rare ; cleavages upon the base and orthopinacoid are 

 sometimes observed. The clino-pinacoidal sections of the mineral 

 show the most intense colours ; the polarization-colours are magni- 

 ficent. The following is the analysis : — 



100-53 



The chemist expresses a doubt as to whether the iron exists in 

 the state of sesquioxide or monoxide. The author then alludes to 

 the difference of opinion as to the state of oxidation of iron in the 

 Swedish and Alpine piedmontites, and suggested that the Japanese 

 mineral supplies a missing link between the two. The Japanese 

 mineral was originally mistaken for tourmaline, and the rock called 

 Tourmaline-schist by E. Naumann. Although comparatively rare 

 both in Piedmont and Sweden, in certain parts of Japan it is so 



