There are three main inliers of Silurian rocks in the Pentland Hills:—

(1) Lyne Water—North Esk Reservoir Inlier, which includes the Gutterford Burn section with the well-known Eurypterid and Starfish beds and the Deerhope and North Esk sections in which there is a passage upwards into red beds often referred to as “Downtonian”.

(2) Bavelaw Castle Inlier, with beds of an age similar to those in the Gutterford Burn.

(3) Loganlee Reservoir Inlier, yielding a few graptolites in strata partly corresponding with those of the Bavelaw Castle Inlier, and with an important assemblage of Silurian corals in the overlying Lower Old Red Sandstone conglomerate.

This year, the 150th anniversary of Hutton's death, we are particularly reminded of the lively struggle of the eighteenth century between Vulcanists and Neptunists; the more so since that struggle finds its counterpart to-day in the divergence of opinion between two schools of petrology whose respective members might aptly be called Magmatists and Transformists. Much of the disagreement between the modern opponents arises from a belief on the part of the Magmatists that Hutton proved the magmatic origin of granite, and, in addition, the disagreement is probably strengthened by a misunderstanding of the views held by Transformists, and by lack of knowledge or experience of the evidence on which they base their conclusions. Indeed, Transformists might be tempted to preface their writings with the following very apposite quotation from Werner (1781):—

“I must here present a request to all who would judge of this theory, or communicate their sentiments on it to the public, viz. to begin by reading through the whole treatise, and then to peruse it a second time, with attention. Such a request will not only appear strange to many persons, but even superfluous ; I find myself, however, under the necessity of making it from the manner followed by some individuals with my book on the external characters of fossils. They have often represented me as saying quite the contrary of what I have expressly written. This may have been done by some, through design, but in by far the greater number of instances, it has happened from that work not having been read through ; and in this manner the public has frequently been led into an error, at least for some time.”

One of the most prominent features of an ice-eroded region is the formation of a number of basins scoured out of the bedrock by the ice and rock frozen into it. When the ice has retreated these basins usually fill up with water, thus forming lakes, and Windermere appears to occupy two small basins scoured out of the floor of a valley which extends to the south as far as Cark, where it joins the coastal plain. It is, therefore, difficult to explain why the natural outflow of the lake should be through the Leven valley, a gorge extending from Newby Bridge to Haverthwaite, instead of through this broad valley which must have existed when the lake was formed (see map).

During recent work for the D'Arcy Exploration Co. the writer found it necessary to attempt to understand the structural history of the Malvern Range. The widespread conception of violent “Armorican” earth movements, almost simultaneously acting in directions at right angles to each other in a relatively small area, did not appear satisfactory. No important tectonic contribution to Malvern literature has appeared since Groom's work published in 1899 and 1900, conveniently summarized in Geology in the Field in 1910. Text books either ignore the problems completely and generalize strangely,2 or say practically nothing about them.3 To separate fact from later theory it was necessary to go back to the original surveys. As a result the writer finds himself unable to accept Groom's conclusion on the age of the movements causing the overturning, and in places imbrication, of the Silurian and Lower Old Red Sandstone rocks on the west side of the range. He is also strongly of the opinion that the evidence for the great Malvern Fault, separating the Trias from the older rocks on the east side of the range, has been much overplayed.

The Amphibole-Schist Series appears to be confined to Malaya east of the Main Range, and it is most abundantly developed in north-west Pahang. It occurs partly in the Main Range Foothills, partly between them and the Main Range granite in the Sua-Kerla-Kelubi-Tempoi river system of the Telom Valley, in the Jelai Kechil valley, in the Sungei Lipis and in the Chembatu-Batu-Cheroh system between Batu Malim and Cheroh, Raub District. So far as is known these crystalline schists do not extend far northwards into Kelantan, and they are likewise but poorly developed south of Pahang in Negri Sembilan. They are everywhere associated with the Arenaceous Formation of the Main Range Foothills, quartzites, quartzite-conglomerates, shales, cherts, phyllites, quartz- and mica-schists, which may be either Triassic according to Scrivenor (1911, 1931) or perhaps older than the adjacent Permocarboniferous shales and limestones according to Service, Alexander, and the writer (Ann. Rep., 1940, para. 39; 1939, 1946). In some areas they lie partly on the Main Range granite (Text-fig. 1).