STRATIGRAPH1CAL WORK 357 



II. In Stratigraphy much of Ramsay's work is so 

 intimately bound up with his labours in structural 

 geology as to be hardly separable. But his two 

 presidential addresses to the Geological Society mark 

 a distinct epoch in stratigraphical work. Darwin had 

 dwelt upon the imperfection of the Geological Record. 

 Ramsay proceeded to indicate the historical meaning 

 of this imperfection. He pointed out the various breaks 

 in the succession of the stratified formations of Britain, 

 and by his wide practical knowledge of the subject, 

 gave it a clearness and significance which it had not 

 before been suspected to possess. He showed that these 

 breaks sometimes consist of actual unconformabilities, 

 arising from disturbance and denudation, and demon- 

 strating a long lapse of time unrecorded by stratified 

 deposits ; while in other instances they are marked by 

 no visible discontinuity of the stratification, but by a 

 sudden and more or less marked change in the fossils 

 characteristic of two apparently consecutive forma- 

 tions. His careful tabulated lists of genera and 

 species that pass from one formation to another finally 

 annihilated the long-lived delusion that each geological 

 system was complete in itself, and was separated, by a 

 general destruction and re-creation of life, from the 

 formation that succeeded it. Accepting Darwin's 

 views on the origin of species, he argued that the 

 relative lapse of time between different formations 

 might be determined by the greater or less distinction 

 between them as regards their organic contents. By 

 this line of argument he was led to the novel and 

 suggestive conclusion that periods of time, of which 

 there was in the geological record of Britain no strati- 

 graphical chronicle, might be much longer than those 

 which were represented by stratified formations. 



