358 SUMMARY OF CAREER CHAP, xi 



These doctrines were by far the most important which 

 had been taught in regard to the principles of strati- 

 graphy since these principles were first determined by 

 the discoveries of William Smith. 



III. Connecting his Stratigraphical with his 

 Physiographical researches comes the series of papers 

 in which he discussed the former existence of Conti- 

 nents, or of terrestrial conditions, during the deposition 

 of the geological record. He dwelt especially upon the 

 red colour of certain formations, their barrenness in 

 organic remains, the proofs of the occurrence of traces 

 of land animals and plants in them, and the similarity 

 presented by them to the deposits of salt lakes or 

 inland seas. In this way he tried to restore in some 

 degree the physical geography of ancient periods of 

 the earth's history. He attempted also, from the same 

 kind of reasoning, to estimate the relative value of the 

 old continental periods, and came to the conclusion 

 that the period which began with the Old Red Sand- 

 stone and closed with the New Red Marl may have 

 been comparable to all the time that has elapsed from 

 the beginning of the deposition of the Lias down to the 

 present day. 



IV. In Physiography Ramsay's work was abundant, 

 as well as remarkably original and important. It may 

 be grouped in three subdivisions: (i) Denudation in 

 General ; (2) The History of River-valleys ; and (3) 

 The Results of the Operations of Ice. 



(i) The early paper on the Denudation of South 

 Wales, published in 1846, in the first volume of the 

 Memoirs of the Geological Survey, was undoubtedly 

 the most important essay on the subject which up to 

 that time had appeared. Much had previously been 

 written on the question of denudation, but it was of the 



