65 
of Edinburgh, Session 1878-79. 
Hauglitonite, which, is a ferrous oxide mica, with little magnesia, 
he finds to he the mica special to most of the grey and pale-coloured 
granites of Scotland; and it also occurs in the diorites of Banffshire. 
This new mica likewise occurs somewhat rarely on the Continent, 
though hitherto unrecognised as a distinct species. 
2. On the Carboniferous Volcanic Eocks in the Basin of the 
Firth of Forth — their Structure in the Field and under 
the Microscope. By Professor Geikie, F.B.S. 
(Abstract.) 
In the introductory portion of the paper a sketch is given of the 
present state of opinion among Continental petrographers regarding 
volcanic rocks associated with palaeozoic formations. The author 
points out that a relic of Werner’s belief in the recentness of volcanic 
action may still be traced pervading the ideas of German geologists. 
In this paper he endeavours to show that, alike in their formation in 
the field and in their structure under the microscope, the basalts and 
tuffs of palaeozoic time were as truly the products of volcanic action 
as the lavas and ashes of the present day. The area selected for 
description is the basin of the Firth of Forth. After an outline of 
the labours of previous observers in this classic region, the author 
sketches the history of volcanic action there, showing that volcanoes 
abounded and threw out an enormous pile of material during the 
time of the Lower Old Eed Sandstone. After a long period of 
quiescence, the subterranean disturbances were renewed in an early 
part of the Carboniferous period, and continued until near the close 
of the deposition of the Carboniferous Limestone series. It is with 
the history and the products of this second volcanic epoch that the 
present communication deals. 
The paper is divided into two parts. The first of these treats 
of the history of volcanic action during the Carboniferous period 
in the basin of the Firth of Forth. That area consists of six 
volcanic districts, in several cases remarkably independent of each 
other ; and, though separated only by a few miles, yet producing 
very distinct forms of lava and tuff. The structure of the volcanic 
rocks in the field is then traced. Detailed descriptions are given 
