the Tertiary Formations. 269 



structed. This deposite is so necessary for the purpose of build- 

 ing in that district, that when it happens to be wanting, or be- 

 comes sandy, as in the neighbourhood of Perpignan, the inha- 

 bitants are reduced to the necessity of building their houses, and 

 even their monuments, of brick. 



If, in our large memoir on the tertiary formations of the 

 south of France, we have admitted the existence of the first ter- 

 tiary limestone, it is because we were deceived by the presence 

 of green grains in the lower beds of the second tertiary lime- 

 stone ; but, since we have found that these grains also exist in 

 the tertiary marine sands, we have perceived that we there gave 

 the green grains a geological importance which they do not 

 possess. 



From these facts, it would appear not only that the seas were 

 already separated at the time when the tertiary formations were 

 deposited, but also that the ocean retired within its present hmits 

 sooner than the Mediterranean ; a fact which seems equally to 

 result from the geological comparison of the Mediterranean and 

 oceanic tertiary basins, as well as from historical monuments. 

 Thus, the more recent geological times are connected with the 

 historical times ; for the period which refers to the tertiary de- 

 posites is probably not remote from the present times, as may be 

 presumed, we repeat, from the numerous species identical with 

 those at present existing, which are found in the newer tertiary 

 strata. 



If the tertiary deposites have been successively produced, at 

 no great interval from each other, and in proportion as the seas 

 retired, it cannot be admitted that the strata, of which they are 

 composed, and whose organic remains announce different habi- 

 tations in the beings which they contain, have been precipitated 

 by different fluids, or by successive retreats and refluxes of the 

 waters of the sea, upon our continents. The facts which an- 

 nounce tile reverse are so numerous, that, for the sake of brevity, 

 I shall only mention one that has pot yet been published, al- 

 though the basin, in which we observed it, has been visited by 

 numerous geologists. 



In the bottom of the valley of Aix (Mouths of the Rhone), 



JULY OCTOBER 1829. T 



