STRAND-LINE DISPLACEMENTS 477 



sion of a continent, so complicated, and divided into so many fragments, with- 

 out any mutual displacement of the parts — a supposition necessary to explain 

 the horizontal course of these lines on the separate portions of a mountain com- 

 plex — cannot be brought into harmony with our present knowledge of the 

 structure of the mountains themselves. Thus this circumstance, too, leads us 

 to infer independent movements of the sea, that is to say, changes in the form 

 of the hydrosphere" (1 : 14, 15). 



In 1848 "Robert Chambers introduced a new phrase ; he spoke neither of ele- 

 vation nor of subsidence, but only of 'changes of relative level,' or, as we shall 

 say, displacements of the strand-line. 



"With the adoption of these neutral terms it at once follows that the dis- 

 placements of the strand-line in an upward direction must be described as 

 positive, those in a downward direction as negative, since this is the terminol- 

 ogy universally employed by all oceanographers and in all operations of water 

 gauging. ... In this work therefore the older term elevation of the land 

 will be replaced by negative displacement of the strand-line and subsidence of 

 the land by positive displacement of the strand-line" (II: 24). 



"Great and general negative movements are from time to time produced by 

 the formation of fresh oceanic abysses, or by the addition of new areas of sub- 

 sidence to abysses already in existence, and it is important to bear in mind 

 that movements of this kind surpass all others in importance" (II: 27).. 



"As soon as we recognize the Ocean basins as sunken areas, the continents 

 assume the character of horsts, and the ivedge-like outlines of Africa, India, 

 and Greenland, all pointing towards the south, find their explanation in the con- 

 junction of fields of subsidence which reach their greatest development in the 

 same direction." 



"The crust of the earth gives icay and falls in; the sea follows it. But while 

 the subsidences of the crust [= lands] are local events, the subsidence of the 

 sea extends over the whole submerged surface of the planet. It brings about a 

 general negative movement. 



"As a first step toward an exact study of phenomena of this kind, we must 

 commence by separating from the various other changes which affect the level 

 of the strand, those which take place at an approximately equal height, whether 

 in a positive or negative direction, over the whole globe ; this group we will 

 distinguish as eustatic movements" (II : 537, 538). 



Suess then surveys the various major transgressions of the sea and the 

 emergences of the land, nearly all of which are recorded in the American 

 continent. He concludes as follows : 



"This recapitulation shows that the theory of secular oscillations of the conti- 

 nents is not competent to explain the repeated inundation and emergence of the 

 land. The changes are much too extensive and too uniform to have been 

 caused by movements of the earth's crust. The middle Cretaceous transgres- 

 sion presents itself on the Amazon, the Athabasca, the Elbe, the Nile, the 

 Tarym, and the Narbada, in Borneo and Saghalien, and on the Sacramento ; it 

 marks a general physical change which affected the whole surface of the planet. 

 In this lies the explanation of the remarkable fact that it has been found pos- 

 sible to employ the same terminology to distinguish the sedimentary formations 



