RAMBLING THOUGHTS IN A HANLEY MARL PIT. 75 



account for the variation in vegetable and animal life may 

 have been mainly the result of changes in the relative 

 position of land and water, and that those changes were 

 extremely gradual, causing, however, peculiarities in every 

 coal basin or field, so that in fact they have been ac- 

 cumulated under different conditions. 



Many of our larger coalfields appear from the admixture 

 of marine shells and animals with land plants to have 

 been probably formed on the shores of an open sea, or 

 in bays of salt water, into which plants had been drifted 

 from the adjacent lands ; others, as that of coal brush- 

 wood, at the mouth of a former large river ; and some 

 of smaller area, being charged with remains exclusively 

 of terrestrial or fresh-water origin, are supposed to have 

 been formed by rivers emptying themselves into lakes. 

 The small field of Shrewsbury is an illustration of this 

 last mode of formation. I shall not stop to discuss the 

 evidence as to the conditions which obtained during the 

 accumulations of the beds forming the North Staffordshire 

 coal-field. There are many members of our society far 

 more conversant with the data necessary to form an 

 opinion on this point ; but I am probably not doing an 

 injustice to any one in especially mentioning the name of 

 one of our number, Mr. John Ward, as one thoroughly con- 

 versant with this question. The fossils so diligently col- 

 lected by him and by Mr. Molyneux and others point 

 apparently to sea water predominating through the greater 

 part of the period, but with a large admixture of fresh 

 water towards the close. I will only say that every coal- 

 field or basin has its own peculiar features. The beds of 

 coal vary everywhere in number and thickness, as do the 

 intervening beds of mud, or clay, and sand. You have 

 heard in South Staffordshire of the ten-yard coal, where 



