COLLATERAL EFFECTS OF UPHEAVAL. 349 



Collateral Effects of Upheaval and Depression. 



Relation of Lines of Upheaval to Magnetic Intensity. M. 



Necker, in a communication to the Societe dHistoire NaturelU de 

 Geneve, traced a very unexpected coincidence over large portions of 

 the northern hemisphere, of the direction of the strata, and the curves 

 of equal magnetic intensity, as drawn by General Sabine. One of 

 these curves, that of 297 seconds, traverses Scotland in a direction 

 north-east and south-west, which is exactly that of the strata. It 

 keeps the same direction by Christiania in Norway, where the strata 

 trends north-east and south-west, and passes through Sweden where 

 the same direction of strata predominates. On arriving at the Gulf 

 of Bothnia the magnetic curve turns north-west and south-east, which, 

 according to Strangways, is the direction of the southern border of the 

 Swedish and Russian granite. 



The curve of 308 seconds enters Europe by Lisbon, and passes 

 south-west and north-east through the Spanish peninsula, which is 

 nearly the line of most of the long sierras between the great rivers ; 

 it passes by the Cevennes, and goes parallel to the Alps in their north- 

 east course to the Tyrol, but there turns south-east, as do also the lines 

 of stratification through Carniola, Istria, Croatia, Dalmatia, and the 

 Morea. Parallel to these are the Carpathian mountains. The same 

 correspondence between the magnetic curve and the lines of folding 

 of strata is traced through the Crimea and along the Caucasus. 



In North America the magnetic curve and the stratification range 

 north-east and south-west along the whole eastern coast ; in the Rocky 

 Mountains both extend from north north-west to south south-east ; in 

 Mexico the magnetic curve takes the parallel of the Cordillera of 

 Anahuac north-west and south-east, and ranges along the south coast 

 of New Spain. Farther to the south the curves resume their course 

 north-east and south-west, which, according to Humboldt, is the direc- 

 tion of the strata in* Venezuela, and between the Orinoco and the 

 Amazons. The chain of the Himalaya, which in Nepaul bears north- 

 west and south-east, and turns north-east at the north-east extremity 

 of Bengal, is parallel to the curve of 297 seconds which was first 

 noticed. Whether the thermal conductivity of strata governs their 

 magnetic intensity, or whether alternation of mineral character governs 

 inductive electrical action of strata on each other, or whether the 

 compressions and tensions of contortion have modified magnetic char- 

 acters of strata, are problems not undeserving the attention of the 

 physical geologist, but too special for examination here. 



Possible Changes in Ocean Level from Depression of Land. 

 The variability of the ocean level in consequence of displacements of 

 the solid land may be stated under three hypothesis : 



First, We may suppose no vacuum to exist below the crust of 

 the earth, nor any receptacle into which the solid land could sink, but 

 that a sinking in one place should be compensated by a rising in 

 another, so that the cubic dimensions of the globe remain unchanged. 



