The species of the Silurian mollusca have changed, but mollusca of Silurian type abound at this hour. Evidence amounting almost to absolute demonstration identifies the _globigerina_ of the Atlantic mud of to-day with the _globigerina_ of the Cretaceous system; and Sir Charles Lyell calculates that the Cretaceous system came to an end 80,000,000 years ago. Pronouncing the types of the past evanescent, Dr. Kurtz pronounces the type of the present permanent. The creatures called into existence on the six days of Genesis, which last he holds to have been natural days, 'were intended to continue, and not to perish, and their families were not to be petrified in strata, but each individual was to decay in the ordinary manner, so that their bones have mostly passed away without leaving any trace.' This is a pure imagination. There is no reason to believe that the petrifactive agencies are less active at present than they were in by-gone geological epochs. The essential and irreconcilable discrepancy, however, between the views of Dr. Kurtz and the conclusions of geology, consists in his assumption of a universal deluge, sweeping away all life, and leaving the surface of the world a _tabula rasa_, immediately before the appearance of man. He speaks of 'a flood, which destroyed and prevented all life, and after the removal of which the present state of the earth, with its plants, animals, and man, was immediately restored.' With marvellous simplicity he declares that 'the only thing' he 'demands,' 'and which no geological theory _can_ or _will_ deny,' is that 'the globe was covered with water' before the appearance of man 'and the present plants and animals.' There is no geologist deserving the name at present alive who would admit this proposition; and we suppose that a large majority of living geologists would maintain that the earth has certainly not been covered with water since the time of those forests whose remains are preserved for us in Devonian strata. To name one among many proofs, the state of the fauna of the Atlantic islands, Madeira and the Desertas, demonstrates that the earth has not been enveloped by the ocean for a period compared with which Dr. Kurtz's 6,000 years dwindle into insignificance. Geology pronounces as decisively against the occurrence of a universal chaos upon earth 6,000 years ago as against the accumulation of all the strata of the earth's crust in six natural days. There is no sense recognisable by geological science in which the word 'beginning' can be applied to the condition presented by the surface of the earth at any period nearly so recent as 6,000 years ago.