462 S. Allport—On PhonolUefrom the "Wolf Roch" 



Ninth. — The deposition of the Boulder-clay and Moraine drifts. 



Tenth. — The " Esker Sea " Period, when the waters of the sea rose 

 ahout 350 feet higher than they are at present, during which time 

 the Boulder-clay and Moraine drifts were in part denuded, forming 

 sand and gravel ridges, sea-beaches and other records of this ancient 

 sea. 



Eleventh. — The waters sank about 250 feet, after which the 100- 

 feet sea-heaches were formed. 



Twelfth. — The waters sank about 75 feet, after which tbe 25-feet 

 sea-heaches were formed. 



Thirteenth. — The waters sank at least 55 feet. 



Fourteenth. — The sea waters rose at least 55 feet, as bogs with 

 " corkers " or roots of trees in situ, occur over 25 feet below the 

 present sea-level. 



Fifteenth. — A probable gradual fall of the sea-level at the present 

 time. 



Y. — Note on the Phonolite fkobi the " Wolf Eock." 

 By S. Allport, F.G.S. 



N the Geological Masazine, Yol. YIII. 1871, p. 247, I gave a 

 short account of the composition and structure of a Phonolite 

 which forms the mass of the Wolf Eock lying between the Land's 

 End and the Scilly Islands. The account there given has been 

 noticed by Prof. Zirkel in a work recently published,^ in which he 

 refers to my description of some of the crystals stated to be nephe- 

 line, and suggests that they may be nosean. The passage tO' which 

 he refers is as follows : — " The grey dust filling some of the crystals 

 is frequently collected together so as to form a dark or even black 

 mass in the centre, the edges of which are sharply defined, and 

 correspond exactly with those of the crystal. Hexagonal crystals, 

 for example, exhibit a border filled with a fine grey dust, and a 

 central portion occupied by a well-defined black hexagon, or there 

 is sometimes a black band running parallel with, and at some 

 distance from the sides." To this I may now add, that some of the 

 crystals and irregular grains are traversed by a number of very fine 

 straight lines of a bluish-black colour, and that with a high magni- 

 fying power these lines are resolved into rows of extremely minute 

 dark granules similar to those forming the dust. This remarkable 

 structure, combined with that previously given, is so thoroughly 

 characteristic of nosean that there can be no doubt of its pi-esence in 

 the rock ; the mineralogical composition of which is thus found to 

 be in complete accordance with that of the large series examined by 

 Zirkel. 



Through the kindness of Mr. Beazeley, of Penzance, I have now 

 a better and more characteristic specimen of the rock than those 

 previously in my possession. It is in a remarkably fresh state of 

 preservation, contains numerous visible crystals of glassy felspar in 

 a compact base, together with many dull blackish grains of nosean. 

 ^ Mikroscopisclie Beschaffeiiheit der Mineralien und Gesteine. 



