(nA37 2) 
XII.—On the Carboniferous Volcanic Rocks of the Basin of the Firth of Forth 
—their Structure in the Field and under the Microscope. By Professor 
GeixiE, LL.D., F.R.S., Director of the Geological Survey of Scotland. 
(Plates IX., X., XI., XIT.) 
(Read 3d February and 2d June 1879.) 
CONTENTS. 
PAGE PAGR 
: PART II.—PETROGRAPHY. 
INTRODUCTION . ; : ; . 438 
I. Tar Crystaniine Rocks or LAvas. 
A. Augite-Felspar Rocks . . 487 
PART I.--STRATIGRAPHY. I, The Diabases or Granitoid Type. 
A. CARBONIFEROUS STRATA OF THE BASIN OF 2 penveal Bx aes, decd 
ee ain FoRrn -: A Chao ii. Microscopie Characters : . 487 
IL. The Dolerites. 
i. General External Characters and Mode 
B. Vorcantc Districts. __ __ of Occurrence . . - 493 
ii. Microscopic Characters : . 494 
1. Edinburgh District . : . 445 Phenomena of Contact . ; . 496 
2. East Lothian District . , . 447 
3. West Lothian District . : . 448 Il. The Basalts. 
4. Stirlingshire District . : . 449 i. General External Characters and Mode 
5. West of Fife District . : . 450 of Occurrence : : . 500 
6. East of Fife District . : . 451 ii. Microscopic Characters . P . 500 
IV. Serpentine-Olivine Rocks.—Pikrite. 
i, General External Characters and Mode 
©. SrRucTURE OF THE VOLCANIC Masszs. of Occurrence : , reso 
Biv clianic Necks ii. Microscopic Characters . : . 506 
General Characters. . - £05 B. Felspar-Magnetite Rocks. 
Materials filling Necks . : . 458 The Porohurites 
Arrangement of Materials : .. 463 Hg ting 
Dykes, Pipes, and Cakes of Lava, &e. . 465 i. General External Characters and Mode 
Junction of Necks with surrounding of Occurrence . : - 508 
Rocks [ ‘ = A PAG Ree c} ii. Microscopic Characters . ‘ > 509 
Evidence of Suberial Onan ; 470 C, Felspar (Orthoclase) Rocks. 
Relation of existing Rocks to former | The Felsites. 
Cones . 471 
Final Stages of Veleanie Meta 473 i. General External Characters and Mode 
ii. Intrusive Sheets and Dykes of Occurrence ; : DRDO 
General Characters : + APA ii. Microscopic Characters . : . 511 
Area and Horizons : ‘ tia ai 
Betton to Volcanic’ Centres. _ 478 Il. THE FRAGMENTAL Rocks or TUFFs. 
Age of Intrusive Sheets ; . 479 | i. General External Characters and Mode 
Dykes . : ee 280, of Occurrence ; é . 512 
iii. Bedded Lavas om Tufts : > 480 | ii. Microscopic Characters . : eDils 
Or 
g 
VOL, XXIX. PART I. 
