tetnjyerature of the interior of the earth. 121 



" 12, Whatever may be the nature of the forces, or the astro° 

 siomical events, which have anciently troubled the stability of 

 coatinents, and produced that general dislocation and overturn- 

 ing which the crust of the earth exhibits, we may easily imagine 

 that all the parts of this crust floating on a fluid mass, and infi- 

 nitely subdivided by stratification, and above all by the innume- 

 rable contractions which cooling has produced in each layer, may 

 have been dislocated and overturned as we actually see has been 

 the case. These effects are inexplicable on the usual supposi- 

 tion of the external strata of the primitive having been last con- 

 soiidated, and the globe being solid to its centre. 



" 13. On considering the probable fluidity of the central mass, 

 the phenomena of earthquakes, the trifling thickness of the con- 

 solidated crust,* and, above all, the innumerable solutions of con- 

 tinuity which divide the crust of the earth, and which result ei- 

 ther from stratification, or from the contraction which takes place 

 during progressive cooling, or from the overturnings which the 

 strata have experienced, we long ago were induced to acknowl- 

 edge that the crust of the earth possessed a certain degree of 

 flexibility. In a memoir read at the Academy in 1816, we de- 

 veloped the elements of this singular property : but that memoir 

 had the misfortune to be presented at a moment when the public 

 mind was not sufficiently prepared to attend to these kinds of 

 speculation. This flexibility becomes now more probable than 

 ever: we ma)' now conceive moreover, in consequence of the 

 fluidity of the central mass on which this crust reposes, how this 

 flexibility may be affected without our being sensible of it. In 

 fact, to bring about a change of figure in the spheroid capable 

 of elevating the equator one metre, it would be sufficient in re- 

 lation to the plane of the equator that each of the innumerable 

 solutions of continuity which intersect transversely the solid 

 crust, and which I shall suppose to be five metres separated from 

 each other on the average, should undergo a separation equal to 

 the 1-1276 part of a millimetre: a quantity extremely small. 



" 14. The probable flexibility of the crust of the earth is ac- 

 tually confirmed by two principal causes: the one general and 

 continual ; the other local and transitory. This last cause, con- 

 sidered during the last thirty centuries which have elapsed, has 

 spared no region of the earth. Sometimes it has shaken almost 

 at the same moment the twentieth part of the continents ; or else 

 it has produced an undulation in directions equal to the sixth or 

 seventh part of a meridian. I allude to earthquakes. Since 



* About the one-one-hundredth part of the semi-diameter of the globe, as- 

 suming the primitive to be forty miles deep. — Reviewer. 



Vol. XV.— _No. L 16 



