86 DR THOMSON ON THE STRATA OF BERWICKSHIRE. 



series. Now I traced a calcareous roclc lying' under the Berwicksliire 

 sandstone (which, it should be observed, is characterized by containing 

 beds of sulphate of lime) for three miles, in a northerly direction 

 from the Tweed at Birgham, and as many to the westward from the 

 same point. In addition to this, I analyzed the rock, and found it to 

 consist of one atom of carbonate of lime, and one atom of carbonate 

 of magnesia, a composition exactly similar to that of the magnesian 

 limestone which occurs on the coast near Sunderland. "What could be 

 the legitimate conclusion from these facts, thun, but that this rock 

 constituted the magnesian limestone formation ; and that whatever 

 sandstones I should find in contact superior to it, would bebjng to the 

 new red sandstone furuuition ? If the magnesian limestone had occur- 

 red only in the form of thin beds of insignificant extent, then it might 

 have been granted, without compromising the claim of that rock to 

 the title of a formation, that the rock with which they were connected 

 was a member of the carboniferous series, or even had its position 

 beneath them : but this was not the case ; and therefore it is as clear 

 as the orb of day when at its meridian brightuess, that if the Ber- 

 wickshire sandstone belongs to a series which is older than the 

 carboniferous rocks, the magnesian limestone is still older than the 

 latter set of strata ; and, further, that the sandstones overlying the 

 magnesian limestone, and which have been hitherto termed new red 

 sandstones, are also older than the coal rocks. Hence it will be 

 impossible to make any distinction between old and new red sandstone. 

 Tliat the Merse rocks are intimately connected with the carboniferous 

 group, is obvious, from the circumstance of our meeting with consider- 

 able remains of plants in the quarry at Whitsom, bearing a strong 

 rjse:ublance to Calamites. But is it not agreeable to what we should 

 expect to meet with, that rocks deposited subsequently over others, 

 should approach somewhat in their nature ? I have already stated 

 this in some botanical observations published in the last number of 

 the Transactions, and written in July or August last year. I have in 

 vain long endeavoured (and many a day have I fruitlessly pursued 

 this important object) to discover a section where the junction of 

 the red sandstone, and decidedly coal rocks, could be detected. But 

 until their relative positions are demonstrated, it would be unphilos- 

 ophical to deny that the Berwickshire sandstone is new red sandstone. 

 Having made these remarks, in order to excite attention to the 

 elucidation of the age of the Berwickshire strata, I proceed to state, 

 that the true coal strata only begin to exhibit themselves on the banks 

 of the Tweed. At Lennelhill, where fossil vegetables have been so 

 unmercifully quarried by amateurs, so as to leave scarce a vestige for 

 the man of science, the only person to whom they could be of the 

 slightest value, the limestone and shale containing microscopic shells 

 are clearly members of the carboniferous group. They occujiy a con- 

 siderable portion of the banks of the river in this neighbourhood ; but 



