REVIEWS — LAKES SUPERIOR AND HURON. 451 



which offered the greatest power of resistance must have also been 

 the most homogeneous possible, at the period when the revolution of 

 the terrestrial globe on its axes was first established. 



" The displacement of bodies, depending on their adaption to the 

 action of fluids (la nature qie'ils possedent pour V action des fluides) 

 must have produced some effect in changing the centre of gravitation 

 in the globe. This being changed, the direction of the poles must 

 also have been altered ; but in its constant rotation the rays of the 

 sun communicating to the terrestrial globe the generative action of 

 the fluids, the metals must have undergone a new arrangement dif- 

 fering from that of the first era, but ever conformable to the com- 

 bined result of the forces, viz : from east to west, from north to 

 south and occasionally from pole to pole {celle des polarisations.) 

 But the fluids meeting in their transit bodies endowed Avith various 

 degrees of fitness as conductors, the direction of the aggregate power 

 of the active forces, to effect the combination and decomposition of 

 bodies, must necessarily have undergone modification, and have ef- 

 fected combinations, greatly varying in their nature. 



" As an effect of the various revolutions which the terrestrial globe 

 has undergone, whether by the alteration of the centre of gravita- 

 tion and the formation of mountains, by earthquakes, the result of 

 an accumulation of fluid arrested in their transit by an obstruction 

 (digue) composed of bodies of various degrees of fitness as conduc- 

 tors, or finally, by the partial action of volcanoes, or by an inunda- 

 tion of greater or less duration contemporaneous with the primitive 

 formation, the decomposition of terrestrial matter must have pro- 

 ceeded irregulai'l}'" (a du subir des licjnes brise'es) and the terrestrial 

 globe must therefore in subsequent revolutions have become less and 

 less homogeneous, in regard both to the nature of its component 

 parts, to their power of resisting expansive forces and to the de- 

 pression produced by the weight of masses. The mountainous for- 

 mations must have been greatly shortened and of unequal height, and 

 metals must, during subsequent changes have been subjected to many 

 various influences, and have performed an almost exceptional part 

 among the more direct and general operations, acting on the great 

 mass of the terrestrial globe. 



" In the present day, after the lapse of many periods characterised 

 by various formations, there is a great difficulty in anticipating the 

 true position, direction and circumstances of combination in which 

 we may expect to find minerals. In order to form a just conclusion, 

 sufficient leisure is necessary to enable the geologist to observe the 

 locality with accuracy, and to study the different action and effect of 



