PROCEEDINGS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. CXXV11 
arranged for the benefit of those who could not be absent from town 
all day. The object was chiefly geological, but some interesting 
plants were observed also. A glance at the geological map will 
show that this glen has special features for study by the geologist. 
The main rock-mass, like the rest of the Sidlaw Hills, consists of the 
beds of volcanic rocks, poured out from a series of volcanoes in the 
neighbourhood during Old Red Sandstone times, and now dipping 
at a moderate angle towards the north-west. Mingled with these 
are beds of conglomerate and of volcanic debris, which are exposed 
in places in the glen. The most striking feature, however, is a trap- 
dyke, or wall of volcanic rock, which has been thrust through a 
fracture in the older lavas at a comparatively recent geological period. 
This Pitroddie dyke is exceptionally conspicuous, as its course for 
more than half-a-mile is parallel with that of the stream, which has 
worn away the older and softer rock, leaving the dyke standing up 
as a great black rampart on the eastern side of the glen. Higher up 
the glen, the dyke, after being invisible for a few hundred yards, re¬ 
appears on the other (western) side of the stream. Here, in a small 
quarry where the ancient lavas (Andesite), the dyke (Basalt), and the 
volcanic detritus (Tuff) were all exposed in section, we came across 
an exceedingly instructive example of the origin of soils from disin¬ 
tegration of rocks, to which I hope to refer in detail on some future 
occasion. Mr. Dow reports on the botany as follows :—“ Among 
a profusion of common plants were found Lychnis viscaria , the 
German catchfly, scarce here, but abundant in Glenfarg; Astragalus 
glycyphyllos , the sweet milk vetch, a noble-looking vetch, found 
sparsely in the Tay valley; Viola hirta , the hairy-leaved early spring 
violet, very similar to the common Viola odorata, the sweet-scented 
early spring violet, but without its perfume; and Polygonum vivi- 
parum , one of the knot-grass family, which forms bulbils on the 
lower part of the flower spike. These bulbils drop off and form 
young plants. Equisetum pratense , one of the more common horse¬ 
tails, which is frequently found in stagnant muddy hollows, was also 
fairly abundant.” 
No. 3, June 13.—To Reekie Linn. Leader, Miss M. Thomas; 
present, 19. This excursion, which was partly geological, partly 
botanical, and partly photographic, was one of the most enjoyable of 
the season, thanks to the kind hospitality of Mr. Thomas and his 
family, who had entertained the Society on the same spot about 
twenty years previously. The “Linn,” or Fall, is caused by a band 
of very hard volcanic rock which crosses the course of the Isla at 
this point, and which looks like a Quartz Porphyry, though as to its 
composition I could not be quite certain. Below the Linn the river 
has cut out an abrupt canon-like gorge in the sandstones and con¬ 
glomerates, forming a striking contrast to the configuration above 
the fall, where there has been very little denudation. Amongst the 
plants found during the day Miss Thomas reports the following:— 
Pyrola minor (not in flower), Saxifraga stellaris , Geranium lucidum , 
Trientalis europcea , Trollius europceus , and Rubus saxatilis. The 
entomologists and photographers also were not idle, the latter 
securing a group of the party, taken in the garden of Mr. Thomas’ 
