100 Proceedings of the Royal Physical Society. 



several layers composing coal seams should each have peculiar 

 structural characters of their own, which are constant over 

 large areas. Nor need we wonder at that curious fact, much 

 insisted upon by Mr E. Wethered years ago, that we hardly 

 ever, perhaps never, find tree trunks extending upwards 

 through coal seams in the position of growth ; which must 

 necessarily have been the normal state of things in the case 

 of coals that have grown in situ. It will also enable us to 

 dispense with the complicated oscillations of level, and that 

 very delicate adjustment of the rate of growth of vegetation 

 to the rate of subsidence, etc., v^hich make so many demands 

 on the faith of young geologists accustomed to think for 

 themselves. 



Some observations were made upon the close connection 

 that exists between seams of coal and beds of ironstone and 

 of impure limestone. It was pointed out that where decom- 

 posing vegetable matter comes into contact with a solution 

 of sulphate of lime, this is decomposed, and carbonate of 

 lime is liberated, if the vegetable matter is in excess. In 

 this way the conditions suitable for the initiation of limestone 

 may be brought about. Where the sulphate of lime is in excess 

 the vegetable matter itself is acted upon; and the author was 

 disposed to regard the amorphous parts of coal as due to this 

 partial dissolution, and subsequent redeposition, of the organic 

 matter. Eeference was made to the bearing of this fact 

 upon the absence of vegetable organisms from Eed Eocks of 

 all asjes. 



The paper concluded with some observations upon the em- 

 ployment of the term Coal-measures. The author advocated 

 an extension of the term so as to include all productive coal- 

 bearing horizons in the Carboniferous rocks, qualifying the 

 term by reference to the age of the rocks containing the 

 coal. 



