A. H. Green — The Permian Beds of 8. Yorkshire. 101 



31 species found in No. 2, which disappeared in No. 3, two reappear 

 here, both excessively dwarfed. With the exception of some doubt- 

 ful traces of plants, these are the only fossils known in this division. 



Such are the facts, the meaning of them I take to be as follows : — 



When the body of water in which these beds were deposited was 

 shut off from the main ocean, some time would elapse before a state 

 of saturation high enough to cause precipitation was reached, and 

 during that time mechanical deposits alone would be formed. These 

 are the Quicksands. One great characteristic of these beds is their 

 irregularity, they occur in patches of various sizes, but are often 

 absent altogether, and they thin out and disappear very rapidly, 

 Their excessive cross-bedding shows too that they were formed by 

 the action of currents. The most likely explanation of these facts 

 seems to be that the Quicksands are the deltas af the streams which 

 emptied themselves into the inland sea. 



After a time the water became sufficiently saturated to cause 

 dolomite to be thrown down to a moderate extent, and the chemical 

 precipitate mixed with the sand brought down by the rivers gave 

 rise to the sandy dolomite No. 2. The conditions, though not 

 favourable, were not such as altogether to prevent the existence of 

 animal life : hence fossils are found, but they are mostly dwarfed. 



As the state of saturation increased preeij)itation went on more 

 plentifully, so that the chemical gained the mastery over the 

 mechanical element, and the purer dolomite No. 3 was produced. 

 The animals could no longer hold their own, and were either killed 

 off, or struggled on in nooks and corners, perhaps a little way up the 

 rivers, where the state of the water was less trying to them. 



Mechanical deposits predominated again during the deposition of 

 No. 4, but the gypsum shows that chemical action was still at work. 



During the formation of No. 5 the magnesian salts had so far dis- 

 appeared, that the water became just habitable; and those hardy 

 species, which had managed to live on, came back, showing, however, 

 by their puny size how hard had been the struggle they had gone 

 through. As far as we know, only two species survived, and it is 

 worthy of note that one of these two is the lusty Axinus duhius, re- 

 markable among the original fauna for its vigour and abundance. 



One point still wants clearing up. Where did the supply of salts 

 come from ? The Permian epoch was one of great volcanic activity, 

 and it was probably from mineral springs produced by volcanic 

 action that the ingredients of the chemical parts of the deposits we 

 have been considering were derived. Thus, though we do not find, 

 as in Scotland and Germany, such convincing proofs of contempora- 

 neous volcanic action as lavas and ash-beds, there is reason to believe 

 that the Permian beds of South Yorkshire are indirectly of volcanic 

 origin. To the same source we must look for the abundant supply 

 of peroxide of iron which gives the colour to the red beds of the form- 

 ation, and it is worthy of note that another formation, still more 

 conspicuously red and also probably of lacustrine origin, the Old 

 Eed Sandstone, was formed during a time when volcanos were at 

 work in Britain. 



