SECONDARY ROCKS— MINERALOGICAL CHARACTERS. 27 



Lothians, in many instances, envelopes beautifully pre- 

 served fishes, while at other times it contains only teeth and 

 scales. Remains of plants, as in all the other members of 

 the coal series, occur in considerable abundance in the clay- 

 ironstone, and on a favourable fracture, they in many in- 

 stances exhibit, in the most perfect manner, numerous and 

 well preserved relics of the flora which existed at that ear- 

 ly period when the coal-beds were deposited. In regard 

 to the position of the organic bodies in the ironstone con- 

 cretions we may remark, that they are invariably disposed 

 parallel to the longest diameter of the mass, an arrange- 

 ment which agrees completely with a deposition from a state 

 of mechanical suspension in water. We have before noticed 

 that the nodules of clay-ironstone are arranged in layers pa- 

 rallel to the direction of the strata in which they occur, and 

 as the shape of these masses is a sufficient indication that 

 they could not have been so disposed in any strata but such 

 as were originally formed in a horizontal position, Ave have, 

 when these lenticular concretions occur in vertical or highly 

 inclined strata, an evident proof that these strata have been 

 altered. The clay-ironstone, which occurs at Wardie, near 

 Newhaven, has lately been analyzed by Dr W. Gregory of 

 Edinburgh (Edinburgh Philosophical Journal, vol. xxxv. 

 p. 17<3). Two of the specimens which were examined by 

 this chemist were found to have the following composition 

 in 100 parts : — 



1. Matter insoluble in acid sand, . 



196 



Peroxide of Iron, 



. 



125 



Alumina, 



. 



35 



Lime (a trace). 







Moisture and Loss, 





44 = 100 



2. Insoluble matter, 





388. 



Peroxide of Iron, 





564 



Alumina, 





25 



Lime (a trace). 







Moisture and Loss, 





33 = 100 



