172 



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EOLOGY. 



[Sect. VL 



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On the other hand, how can we believe that lakes, allow- 

 ing of course their beds slowly to pink, could contain the 

 enormous thickness^ amounting in some instances to 



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;pot, or 



several thousand yards, of the coal-bearing strata ? i: oiu 

 these few remarks it will be seen how many points de- 

 serve careful examination in any nevr coal district ; the 

 chief points being, the presence of upright vegetables and 

 trunks of trees (of the position of which careful drawing 

 should be made), and whether furnished with roots,~the 

 nature of the beds on which the coal rests, and generally 

 of all the strata ; the continuousness and form of the 

 strata, and whether ripple-marked ; the existence of 

 marine animal remains, and whether such lived on the 



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were drifted into their present posiUuns, and 

 many other similar points. It is superfluous to observe 

 that all fossil plants should be collected ; those found 

 upright should be carefully distinguished from those em- 

 bedded horizontally. The contents of any upright stems 

 and of the roots should be examined ; as it appears they 

 have generally first become hollow from decay^ and then 

 been filled up v/ith mud, which in some instances is 

 charged with seeds and leaves. 



Salt Deposits -—luiormdition is much required on this 

 subject ; and tins is a case in which good suites of speci- 

 mens, illustrating the nature of the rocks beneath and 



above the salt, would possess much interest. Do they 

 rontaiii any organic remains? Did such live on tl^ spot 

 where now buried ? Do the rocks show sisrns of having 



undergone in any degree the action of heat ? Are the 

 strata regular, or are they crossed by obhque layers, 

 rfiov/ing the probable action of currents ? Are tLv.re ripple- 



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