Professor Geikie on the " Fitchstone " of EsMale. 233 



formations. But beyond the fact that the greywacke and 

 slate are the oldest formations over which come the " inde- 

 pendent coal formation," and the "newest fioetz-trap," he 

 gives hardly any indication of the geological structure of the 

 country. Each variety of rock is described with care, but 

 with reference to the Wernerian sequence rather than to 

 their relations to each other as constituents of the rocky 

 crust. In particular, the interesting lava beds interstratified 

 at the base of the Carboniferous series of the south of Scot- 

 land are dismissed in three pages, in which their position over 

 the red sandstones and their trend from the Annan to the 

 Esk are the most important circumstances narrated. In this 

 and the other geognostical productions of the time the writers 

 kept before them two main subjects of inquiry — the minera- 

 logical nature and varieties of rocks and their superficial dis- 

 tribution. The Wernerian sequence of formations settled 

 the order of succession among the rocks, and happily put out 

 of sight those problems of geological structure which every 

 field geologist must now grapple with at the outset. 



In the course of his examination of Dumfriesshire, Jameson 

 came upon the " pitchstone" which has been already referred 

 to. He was disposed to consider his discovery of it as a 

 matter of some importance, for he mentions it among the 

 more notable results of his survey. As his description of the 

 rock, besides its connection with the subject of the present 

 communication, is a fair example of Wernerian geognosy, I 

 give it here in full. 



'' At Todshaw HiU, and the hills called Castle Hill, Watch 

 Craig, and Wat Carrick, near the manse of Eskdalemuir, 

 which are composed of compact greywacke, there are several 

 summits covered with greyish -black -coloured pitchstone. 

 The pitchstone is unstratified, and lies over the much 

 inclined strata of greywacke. In the same hills there is 

 porphyry slate which, like the pitchstone, occurs in globular 

 and columnar distinct concretions. Sometimes contem- 

 poraneous masses of pitchstone are to be seen enclosed 

 in the porphyry - slate or basalt, and globular distinct 

 concretions, whose centres are pitchstone, but the sur- 

 faces of a substance much resembling porphyry-slate. We 



VOL. v. Q 



