Notices of Memoirs — B. Bell — Glacial Epoch. 217 



The normal porphyrites are probably microlitic forms of the diabase, 

 just as the nephelinites with which the former are associated (occur- 

 ring especially at the Mile End Quarries) are of the teschenites. At 

 St. Anne there is a melilite of the same age as the other rocks of 

 this group — a point of interest, as this variety has hitherto been 

 regarded as confined to the Cainozoic. 



The dominant type of the nepheline syenite is a rock with granitic 

 structure and composed of grey or pink felspar, nepheline, sodalite, 

 amphibole, pyroxene, and mica. The complete list of minerals 

 numbers twenty-one, and these are all described in detail; the altera- 

 tion products are similar to those of Pouzac. There are also some 

 pegmatitic veins. Amongst the most important points in the memoir 

 are those connected with the contact alteration of the rock : at places 

 the normal structure is retained at the junction, but in other cases 

 the rock is profoundly altered for a distance of some metres ; the 

 variations afford a complete transition from the granitic (grenu) to 

 the trachj'tic types of structure, i.e. from the normal syenite to the 

 " microsyenite " — a term he proposes owing to the analogy between 

 this rock and the microgranites. The large dyke gives off small 

 branches which traverse the limestone, and these are often composed 

 of many alternating zones of the granitic and trachytic rocks. These 

 dykes further lead to the mica porpliyrites ; the sodalite and nepheline 

 are absent either owing to original poverty in soda, or to the greater 

 influence of the endoraorphic alterations on these thinner veins. 

 The extent of the alteration of the limestone at the contact varies 

 greatly ; the minerals developed in the limestone are diopside, 

 wollastonite, garnet, perowskite, and more rarely biotite, sphene, 

 zircon, and felspars. The junction is sometimes marked by a band 

 of cancrinite ; but when the felspar is abundant, a zone occurs which 

 may belong to either the eruptive or metamorphic rock. 



The memoir is illustrated by twenty-six figures of rock-sections, 

 while the great range in the variations of the rocks is further well 

 brought out by the abundant use of M. Michel-Levy's formulas. 

 M. Lacroix, it is interesting to note, rejects at the outset the use of 

 the term ela3olite s^'enite, and he lays special stress in his concluding 

 paragraph on the identity in structure and mineralogical composition 

 of rocks of Silurian age in Canada with those intrusive in the 

 Cretaceous Limestone of the Pyrenees. J. W. C 



IV. — Phenomena of the Glacial Epoch. Part II. The Great 

 Submergence. By Dugald Bell. Trans. Geol. Soc. Glasgow, 

 Vol. IX. pp. 100-LS8. 



BY this Memoir the author has added another name to the 

 growing list of papers written in opposition to the supposed 

 glacial submergence of England and Wales to the depth of over 

 1300 feet. He summarizes all the evidence in favour of this view, 

 and then subjects it to a careful examination, with the result of 

 dismissing it as absolutely valueless. A submergence of 500 feet 

 is admitted, but this the author attributes to the elevation of the sea- 

 level by the attraction of the polar ice-cap heaping up the water in 

 the northern latitudes. J. W. G. 



