Notes on the Igneous Rocks. 4f>5 



of being classed with the Peridotites, to which they are not 

 related, under the general heading of " Kocks containing 

 no Feldspar," have been placed immediately after the 

 Orthoclase Nepheline (or Leucite) rocks and before the 

 Plagioclase Nepheline (or Leucite) rocks. In this way all 

 the rocks containing Nepheline and Leucite are kept to- 

 gether in the table, instead of being separated as before by 

 the Diorites and Gabbros, which are much more nearly 

 related to the Pyroxenites and Peridotites which now suc- 

 ceed them. 



In the Heidelberg collection, moreover, the Diabases 

 have been placed among the Volcanic rocks instead of with 

 the Plutonic rocks. The anomalous position of these rocks 

 when classed as Plutonic rocks — shown by the frequent 

 occurrence in them of amygdaloidal structure, their 

 stratigraphical position as flows and their association with 

 tufa — was always evident, their character, as well as their 

 structure, show that they should be classed among the old 

 Yolcanic rocks. 



The Tinguaites, as well as some of the Acmite Trachytes 

 and the Alnoites in this collection, have also been placed 

 among the Dyke rocks. 



Since the publication of the second edition of the " Mas- 

 sigen Gesteine," moreover, a number of massive igneous 

 pyroxenic rocks occurring in different localities have been 

 accurately studied by several petrographers. ' 



This has necessitated the enlargement of the table and 

 the separation of the Pyroxene rocks from the Olivine 

 rocks with which they were formerly classed. These have 

 accordingly been erected into a new group — the Pyroxen- 

 ites — a name first applied by Dr. S terry Hunt, in 1862 (see 

 Geology of Canada, 1863, p. 667, etc.), to certain eruptive 

 rocks from Eougemont, Montarville and Mount Eoyal, 

 members of a series of old volcanic cores situated in the 



1 Hatch— Quart. Jour. Geol. Soc, May, 1839. 

 Teall— British Petrography, pi>. 71 and 84. 

 Ilutton— Roy. Soc. New South Wales, August, 1889. 

 Williams— American Geologist, July, 1890. 



18 



