Geological Gleanings. 131 



in the course of my geological researches, that certain rocks below 

 the lowest beds of the lower Carboniferous Limestone conformed 

 to them, and contained the same fossils, I was led to add them to 

 the Carboniferous system, the boundary at the base of the Moun- 

 tain Limestone, as it had until then been termed, being found to be 

 far too limited. These lower rocks I was ultimately led to consider 

 as divisible into two groups, the upper of which I proposed to call 

 Carboniferous Slate, and the lower, Yellow Sandstone. In res- 

 pect to this latter and lower of the two series, it became a question 

 as to where the line of division between them and the red beds 

 lying conformably beneath should be drawn ; and the discovery 

 of certain plants, apparently of Carboniferous type, and at present 

 known as Sphenopteris Hibemica, Lepidodendron minutum and 

 Griffithii (the last of which was discovered by Dr. Carte in the 

 course of the last year), led to the adoption of the lines of boun- 

 dary which have been published on the last, as well as on previous 

 editions of my geological Map. 



" Subsequently, through the researches of my friends, Professors 

 Haughton and Jukes, as well as those of myself, imperfect casts 

 of these plants were found very far beneath the boundary which 

 I had originally adopted, and hence the extent of the district which 

 I had allotted to these lower Carboniferous rocks will be found 

 much too circumscribed. The principle, however, upon which I 

 set out, remains intact, and as often contended for, both by Pro- 

 fessor Haughton and myself, in numerous papers, I would again 

 say, that the base of the Carboniferous system will extend to any 

 zone of these plants, no matter at what depth, or in connexion 

 with what rocks soever, found. That this may have the effect of 

 sweeping the whole of the fish beds of Scotland, with the similar 

 rocks of Glamorganshire in Wales, hitherto considered to be De- 

 vonian, into the Carboniferous system, I am not prepared to deny, 

 as it is only a natural inference from the principle which I have 

 laid down. It is true that I have preserved the established terri- 

 tories of the Old Red Sandstone on my Map, curtailing it only of 

 the Plant or Yellow Sandstone beds, as I was not prepared to risk 

 a controversy, merely upon the grounds of the well-known con- 

 formity between the two series, without a sufficiency of fossil 

 evidence, — statements founded upon the hypothesis, no matter 

 how well grounded soever they may appear, but upon less than 

 indisputable scientific principles, being still open to the charge of 

 being mere speculation or guess ; and especially as I found that 



