160 Physical Geography. 



The succession of events that, through the Rhgetic 

 beds, marked the transition from the New Red Marl to 

 the Lower Lias seems to have been as follows : 



In the latter part of the Triassic epoch, as already 

 stated, our Keuper, or New Red Marl, beds were depo- 

 sited in an area that now forms part of England, and 

 this area was in those days a great salt lake. 



This lake gradually got partly rilled with sedi- 

 ments, and by-and-by, through change in amount of 

 rainfall, or through increase of heat, it ceased to have 

 an outflow, evaporation being equal to, or greater than, 

 the influx of water. Concentration and precipitation of 

 salts ensued as already explained. 



Subsequently, during deposition of the marly sedi- 

 ments, by increase of rainfall, or climatic change of 

 temperature, the water became somewhat less salt, but 

 still sufficiently saline, by evaporation of the moisture 

 on wet surfaces, to produce crystals of salt (now pseudo- 

 morphs) in sandy layers interstratified with the marls, 

 together with layers and nodular masses of gypsum, 

 which state of affairs continued up to, and even during, 

 the deposition of recognised Rhsetic strata. That 

 Jxhaetic areas got dried by temporary exposure is certain, 

 lor besides the pseudomorphs, sun- cracks are common in 

 the strata. 



In our area, sinking of the district took place at or 

 about the time when the lake or lakes got nearly 

 filled with sediment, and a partial influx of the sea over 

 shallow bottoms was the result. The deposits that 

 ensued, accompanied by a small migration of marine 

 forms of life, constitute the Rhaetic beds of England. 



Many years ago, the late Professor Edward Forbes 

 stated to me that the fauna of the White Limestone 

 of Lyme Regis, then called White Lias, reminded him, 





