80 Transactions. 



SPECIAL REPORT ON THE GEOLOGICAL FEATURES OF 

 THE DISTRICTS VISITED BY THE MEMBERS OF THE 

 DUMFRIES NATURAL HISTORY SOCIETY DURING 

 THEIR SUMMER EXCURSIONS IN 1878. By Dr 

 Gilchrist. 



Read Nov. 1st, 1878. 



As considerable geological uniformit}'^ exists in the 

 several disti-ict.s visited, it will save much repetition to give 

 a brief general description of them, leaving details to be 

 noticed in the successive excursions. 



1. The piominent rock forming the basis of the hill 

 system of the Soutii of Scotland is the so-called Silurian, 

 constituting the various well-known groups of hills in the 

 neighbourhood, as the Tinwald, Mouswald, Galloway groups, 

 &c. It formed a noted feature in every one of the places 

 visited. 



2. A second variety of rock not unfrequently seen in the 

 neighbourhood is the so-called Permian. It is characteristic 

 as well of the subordinate as of the main valleys in the dis- 

 trict, which forms the subject of consideration, in most of 

 which at least fragments of it will be found where it has not 

 been entirely swept away by denudation. It will be readily 

 recognised in the sandstone quarries of Locharbriggs, Craigs, 

 &c. 



3. A third feature of the districts visited is the result of 

 the so-called glacial action in the form of glaciated rock and 

 glacial till. These are seen much less frequently, though 

 not at all uncommon, the former especially in its ruder 

 aspects, which are easily recognised iu the so-called Roches 

 Moutonees, constituting a series of rounded smooth rocky 

 knolls not unfrequently seen in certain districts. The till is, 

 as a rule, only seen in natural or artificial sections of the .sur- 

 face. It consists of a matrix of clay with fragments of rock 

 of all sorts and sizes irregularly intersjiersed through it, being 

 smoothed, striated, and more or less rounded. In its typical 

 form at least once seen it is easily afterwards recognised. 



4. A fourth feature of the districts visited is the super- 

 ficial accumulations of gravels and sands, the result of 



