154 P. A. ØYEN [1914 



linger i klimatet kan interferere paa de forskjelligste, men vist- 

 nok lovbundne maater med jordskorpens bevægelse, likesom de 

 ogsaa kan interferere indbyrdes, ofte paa en saa indviklet maate 

 at vi helst saa, vi kunde trække os tilbake fra forsøk paa ana- 

 lyse og forklaring af fænomenet. Men istedet for at trykke os 

 ned i en mørk og dyp skepticisme, bør disse vanskelige proble- 

 mer stimulere os til nyt og fortsat arbeide, og inspirere nye 

 tanker og ideer til sammenknytning af fænomenerne. 



Isostase. 



»What are the foundations of the earth? On what do moun- 

 tains, continents, and ocean basins rest?« er de to spørsmaal, 

 hvormed Bailey Willis indleder sin afhandling: »What is Terra 

 Firma? — A Review of current Research in Isostasy« (Smith- 

 sonian Report, 1910, pag. 391 flg.). Henimot slutningen af sin 

 redegjørelse ytrer han paa en merkelig, tidssvarende maate føl- 

 gende: »Isostasy and rigidity both are conditions of the earth's 

 mass. Their relative effects in the changes of stress in the earth 

 varj^ with the state of uplift or erosion, and it is an interesting 

 coincidence that intelligent research should investigate the con- 

 dition during an epoch when equilibrium is most nearly com- 

 plete and rigidity least severely stressed. But we may not over- 

 look the fact that this condition is but a transient one (L. c. 

 pag. 405). Og han afslutter sit arbeide med følgende: If we apply 

 these considerations to the question with which this review 

 began, what are the foundations of the earth? We may answer: 

 The foundations are solid rock, which is selfcrushed to a depth 

 of 120 kilometers, more or less, which is rendered sufficiently 

 rigid by pressure to maintain its form during prolonged geologic 

 periods with but very slight change, in spite of stresses occa- 

 sioned by erosion of continental reliefs, but which is capable 

 of movements that from time to time result in the gradual ele- 

 vation of continents and the more vigorous uplifts of mountains 

 through which isostatic equilibrium is restored« (L. c. pag. 406). 



Men vi kan gaa langt tilbake, tilbake til kvartærgeologiens 

 grundlægger Hutton, for at finde spiren til de tanker, som oven- 

 for blev uttalt. »Playfair, in his »Illustrations of the Huttonian 

 Theory ', in 1802, admitted the sufficiency of the proofs adduced 

 by Celcius, but attributed the change of level to the movement 

 of the land, rather than to a diminution of the waters* (Charles 

 Lyell: Principles of Geology, 4th edition. Vol. II, 1835, pag. 335). 



The hypothesis of the rising of the land, he adds, »agrees 

 well with the Huttonian theorv, which holds that our continents 



