216 Notices of Memoirs — Syenites, etc., de JPonzac. 



salt. Mr. Howse attempts to prove the identity of the Upper Lime- 

 stone in the salt-borings in South Durham with the Brotherton 

 Beds in South Yorkshire, and the identity of both of these with the 

 Plattendolomit of Germany. He also regards the lowest deposit 

 of Rock Salt as of Permian age. The second contribution is a 

 "Catalogue of the Local Fossils in the Museum of the Natural 

 History Society of Newcastle-upon-Tyne," which occupies sixty 

 pages, and was orginally issued as a separate publication at the time 

 of the British Association Meeting in 1889. This is interspersed 

 with numerous notes on stratigraphy, which are rendered invaluable 

 by Mr. Howse's long experience in the detailed study of the district. 

 The localities from which the specimens were obtained are men- 

 tioned under each species, and a reference is given to the record of 

 its occurrence when already published. 



HI. — Description des Syenites nepheliniques de Pouzao 

 Hautes-P.trenees) et de Montreal (Canada) et de leurs 

 phenomenes de contact. By M. A. Lacroix. (Bull. Soc. 

 geol. France (3), xiii. 1890, No. 7, pp. 511-58, pis. ix.-xii.) 



THE many important contributions to our knowledge of the 

 nepheline syenites made during the past few years by Brogger 

 Tornebohm, Van Werwerke, Derby, and others, have received an 

 important accession in the above Memoir by M. Lacroix. He here 

 describes in detail the nepheline syenites of Pouzac and Montreal 

 and their contact phenomena. At the former the rock is intrusive 

 into a limestone, which is probably Cretaceous ; the rock is of 

 especial interest in connection, with the alteration products. Thus 

 the nepheline has given rise to (1) zeolites such as mesotype and 

 hydronephelinite ; (2) to white mica (gieseckite) ; (3) to garnets 

 (of the ouwarowite type), which either replace the whole of the 

 nepheline or are developed along the cleavage-planes ; (4) to 

 cancrinite ; the amphibole (barkevicite) is altered to green mica, 

 and the pyroxene is often surrounded by a zone of aegyrine. On 

 the selvage the rock passes into a variety in which the magnetite, 

 apatite, sphene, etc., and the ferromagnesian minerals (that is to say, 

 those of the first two phases of the first stage of consolidation) are 

 absent, and the sodic minerals (nepheline and sodalite) are replaced 

 by a felspathic microlitic growth ; the result is a rock comparable 

 to the tinguaites of Prof. Rosenbusch, which in Brazil and Portugal 

 are regarded as apophyses from nepheline syenite. Dipyre, actino- 

 lite, and pyrites occur in the limestone at the contact. 



The nepheline syenite of Mont Koyal, Montreal, pierces the 

 Trenton limestone, and is itself of Silurian age. It is the principal 

 member of a group of igneous rocks which includes some diabases, 

 teschenites, and porphyrites. The diabases and teschenites both 

 belong to a series resulting from the solidification of the same 

 magma ; the teschenites differ from the diabases in the presence of 

 nepheline and sodalite ; when olivine also occurs, the rock becomes 

 one of the true teschenites (of Fouque and Michel-Levy) or theralites 

 of Rosenbusch. 



