466 



THE GEOLOGIST. 



In no single locality do we find a section in wliicli all the beds 

 occur in regulai' and uninterrupted succession ; the absence of some, 

 or the thinning-out of others, constitute local differences which should 

 always be expected and duly considered. Thus, in Lanarkshire 

 generally, as well as in other parts of the Clydesdale coal-field, the 

 strata composing the Carboniferous system have been divided into 

 four principal groups ; and I am indebted to a friend in Carluke for 

 the section here given, and which we will describe in the descending 

 order. 



I. The Upper Coal-seeies, mea- 



suring in some localities 

 about one hundred and fifty- 

 nine fathoms. It consists of 

 eleven seams of workable 

 coal and numerous smaller 

 seams (among which we may 

 name that which has been 

 designated as the " Ell coal," 

 and which is situated to- 

 wards the top of the group), 

 of sandstones, for the most 

 ■part white in colour, or white 

 ■wdth dark sti-eaks, of fire 

 clay and shales, a bed of 

 freshwater limestone, and a 

 few important bands of ii^on- 

 stone. 



II. The Upper Limestone-series, 



about one hundred and 

 twenty-five fathoms in thick- 

 ness, consisting of three 

 limestone beds, but no work- 

 able coal, although there are 

 several thin seams, several 

 bands of ironstone, occasion- 

 ally gTitty — and in the lower 

 pai't sandstone of a yellow 

 colour, fire clay, and shales. 



III. The Lower Coal-measures, 

 about thirty- seven fathoms 

 in thickness — consisting of 

 four workable seams, the un- 

 demiost being the " cannel"- 

 or" gas- seam," so weU known, -{ 

 and several other smaller 

 seams ; sandstones white and 

 sometimes yellow ; fii'e-clay, 

 shale, & a few ii'onstone bands . 



Horizon of the " Ell Coal" 



(In this column are enumera- 

 ted the fossiliferous strata where- 

 in Brachiopoda have been found 

 in the parish of Carluke, and 

 which will be hereafter referred to 

 when we treat of the species. 

 The position is given at so many 

 fathoms below the horizon of the 

 " Ell Coal," but it would be quite 

 as easy to take the space from the 

 horizon of the " Productus gigan- 

 teus limestone" upwards.) 



'"Slaty-ii'onstone, 160 fathoms, 

 below EU Coal. 



Thomson's BaUs 173 „ 



Gare limestone 239 „ 



Belston Bum lime- 265 „ 

 stone. 



^Belston-limestone 283 „ 



Maggy ironstones 300 



