NOTES FROM THE SOCIETY'S NOTE-BOOKS. 239 



[We much regret that no drawing has been made to record the 

 beauties of this extraordinary sUde, and insert the notice simply to 

 inform our readers what may be found, after careful search, in 

 some of the Carboniferous Limestone Nodules. — Editor.] 



Section of Limestone.— This is decidedly oolitic, and has very 

 much the same structure as the Bath Oolite. How has this struc- 

 ture been produced ? There must have been something to attract 

 the lime (segregation) into concentric layers, although nothing is 

 now to be seen within, other than crystals, whilst some of the 

 granules are mere empty shells. This question of the origin is one of 

 the open questions before geologists, and for my part I have never 

 met with a satisfactory solution. I think that the granular structure 

 is an after production, as the granules have no appearance of 

 having been rolled about in water. Some of the concentric layers 

 are very crystalline, and some granules contain crystals within. To 

 account then for the formation of the granules, I should suppose 

 that the carbonate of lime composing the granules, was in solution 

 either in very cold water, deep water, or water containing more 

 than usual of carbonic acid. This would amount to almost the 

 same thing, as cold water holds more carbonic acid than warm 

 water, and it has been ascertained that deep water contains more 

 dissolved carbonic acid than shallow water. (This opens up the 

 question as to whether oolitic limestones are deep or shallow water 

 productions.) 



The next stage would be the separation of the carbonate of lime 

 from the water, leaving it in a solid form, and its formation into 

 granules having concentric coats. This would be a process of 

 segregation, but what could be the central point of attraction ? In 

 some books it is stated that foreign particles, such as flint, grains of 

 sand, fragments of fossils, etc., can be seen within the granules. I 

 can only say I have never seen them, although I have examined 

 the structure for many years. Possibly some foreign substance was 

 within each granule at one time, but nothing can be seen there 

 now. 



I think the structure must be classed with concretions in general, 

 such as we see in various formations, e.g., the clay-ironstones of the 

 coal measures. Whilst rocks are soft and yielding, the impurities 

 contained in them have a tendency to collect together into concre- 

 tions. The diatoms which must be disseminated in all rock 

 deposits, would thus collect together into siliceous masses still 

 microscopic. Much of this siliceous matter would be dissolved if 

 the water or rock became warmer. It is a fact, that if we mix silica 

 with a solution of carbonate of lime, and afterwards heat the 

 mixture, the silica will partially dissolve, and the lime will be 



