during the Year 1828, : I .413 



ations, but the last two have not yet terminated this part of 

 iheir labours. The structure of the mountain is of fresh- 

 water limestone, resting upon granite, with strata of sand 

 alternating with layers of volcanic remains, and crowned by 

 enormous masses of these same remains. Notwithstanding 

 the volcanic productions all round, the formation of this 

 mountain must be referred to that named diluvium, as the 

 bones found are the same as those which characterise this 

 formation, and it is so rich, and contains so many species, that 

 it must always be one of the most remarkable monuments of 

 ^ former world. But in this same country are still older 

 formations, made by fresh water, and containing layers of 

 sand, which present us with different genera. Among these 

 are found many remains of birds (in which Auvergne is ge- 

 nerally abundant), and even some of their eggs, in beautiful 

 preservation. In these places there are no marine beds, the 

 bones are scattered, not rolled, and are often mingled with 

 fresh-water shells. 



M. Adolphe Brongniart, who has devoted himself with such 

 extraordinary zeal and perseverance to fossil botany, has been 

 obliged to create a new^ method of ascertaining the nature of 

 vegetable deposits, and has formed it from the surface and 

 composition of the stems, the nerves of the leaves, &c. &c. 

 He has commenced publishing a new work, where he describes 

 more than 500 fossil species, with their positions. By help of 

 these species, he establishes a certain number of successive 

 formations, in which vegetables succeed each other with few 

 changes, and in almost equal numbers of genera ; and other 

 formations, where genera and families undergo the most 

 sudden changes and bear no affinity to each other. By means 

 of these rapid changes, he has fixed certain vegetable geolo- 

 gical periods, which he has reduced to four; during each of 

 which vegetation has presented but few remarkable changes, 

 but the passages of which from one to another have been 

 strongly marked. The first comprehends transition earths 

 and coal, the second speckled sandstone, the third extends 

 from the upper part of shelly Hmestone to the under chalk, 

 and the fourth corresponds with the tertiary formations. These 

 are separated by strata, which contain few or no vegetable 

 remains ; as the red sandstone and the alpine limestone, which 

 intervene between the first and the second ; the secondary 

 limestone, between the second and third ; and chalk between 

 the third and fourth. In the first period the ferns and the 

 larger vegetables predominate ; in the second is an equal num- 

 ber of ferns, monocotyledons, and Coniferae, but of a smaller 

 size than in the first; in the third the Cycadeae are most 



EE 3 



