Notice on the Magnesite of the Paris Basin, and 

 of the position of this rock in other places. * 

 Bt/ Alex. Brongniart, Mejuher of the 

 Royal Academy of Sciences, 8^c. 



Read to the Royal Academy of Sciences, April 1, 182?. 

 (Annales des Mines, 1822.) 



The distribution of the rocks and minerals entering intq 

 the composition of the crust of the globe, may be regarded 

 in different points of ■view, and the different kinds of relar 

 tions subsisting between these bodies successively examined. 



Sometimes we take a formation composed of different 

 kinds of rocks, whose epoch of formation is well deterniin<i'«J 

 in one place, and we follow it in other parts of the globe, to 

 see if it prci^erves the same position, and to study the mlne-r 

 ralogical modifications it experiences : this point of view is 

 principally/ geological and seco/idarilj/ mineialogical. Some- 

 times we study a simple or mixed rock, of a certain nature, 

 and following it in different places or in the different format 

 tions ill which it occurs. Me examine at what epochs it has 

 been deposited on the surface of the globe, what are the m\-, 

 nerals and rocks with which it is associated, and what pecu- 

 liarities it presents in each of tliese epochs. This point of 

 yiew 'k principally mineralogical and secondarily geological : 



* This paper is perhaps more mineralogical than geological, yet as it 

 involves geological considerations I conceived that it would not be out 

 of place in this selection. (Trans.) 



