Rev. A. Irving— On the Permian and Trias. 219 



Neither alumina nor lime appears to be present in this meteorite, 

 and augitic and felspathio constituents are consequently absent. Tlie 

 oxygen present in the two silicates amounts to — 



SiHcicacid 17-19 30-22 



£l™S°^.'' ::: iKl}='«-5'- - {til} ;■■ = "■»<= ^ 



The soluble portion, therefore, is an olivine, having approximately 



the composition represented by the formula 2(f MgU, ^ FeO), SiOj; 



and the insoluble part a bronzite of the form (§ MgO, ^ FeO), SiOa,* 



the ratio of iron oxide to magnesia being the same in both silicates. 



{To be continued in our next Number.) 



V. — On the Classification of the European Eocks known as 



Permian and Trias. 



By the Eev. A. Irving, B.Sc, B.A., F.G.S. ; 



Senior Science Master of "Wellington College. 



{Continued from liage 164.) 



(c) In the Midland Counties the rocks mapped as Permian are 

 considered on all sides, if Permian at all, to belong to the Lowei' or 

 Eothliegende series ; we need not therefore stop to discuss them at 

 any great length here. The chief authorities are Mr. Howell ^ and 

 the late Prof. Jukes.^ In Warwickshire the case is a simple one : 

 there is, according to Mi\ Howell, a general unconformity of the 

 rocks called Permian with the Triassic strata which lie above them. 

 In the Staffordshire area the case is somewhat different. After a 

 careful perusal of Mr. Jukes's Memoir, I fail to find that his survey 

 of the district enabled him to furnish any direct evidence of the 

 unconformity between the Permians and the Trias, in the existence 

 of which he expresses his belief in the text. It seems that the 

 unconformity in this case is purely hypothetical. He conceives 

 what would have taken place if extensive denudation had intervened 

 in that area between the deposition of the Permian and Trias ; but 

 the facts mentioned by him may be equally well explained by 

 conformable overlap of the Permians by the Trias, unless the Permian 

 strata were themselves conformable to the Carboniferous series : this 

 is shown clearly not to be the case. It would seem that the author 

 was himself only half-convinced by the arguments he had put 

 forward, for in the reduced section (No. 7), at the end of the 

 Memoir, the Triassic strata are represented as lying conformably 

 upon the Permian. 



{d) A very interesting paper, which seems to me an important 

 contribution to the science, has lately appeared. The author of it is 

 Mr. D. C. Davies, F.Gr.S.^ In this paper he has collaborated a large 

 number of facts gleaned from actual sections in which the rocks 

 known as " Upper Permian " occur. The paper is worthy of the 



1 Geology of the Warwiclshire Coal-field, by H. H. Howell, a "Survey "Memoir. 



2 Memoir on the South Staffordshire Coal-field, by J. B. Jukes, M.A., F.R.S. 



3 Vide Q.J. G. S. vol. xxxiii. On the Relation of the Tipper Carboniferous Strata 

 Cf Shropishire and Derbyshire to the Rocks usually classed as Permian. 



