390 Mr. Weaver on M. Alcide d'Orbigny's View 



Appendix. 



Closely connected with the preceding subjects is the valu- 

 able Memoir of M. Alcide d'Orbigny, which has recently ap- 

 peared, entitled, " On the Foraminifers of the White Chalk of 

 the Paris Basin*." The subjoined extracts may serve to con- 

 vey a view of the general scope of the work, which, placed in 

 parallel with that of Dr. Ehrenberg, cannot but excite a dou- 

 ble interest in the mind of the reader. 



Previously to entering upon the direct object of the Memoir, 

 M. d'Orbigny indulges in a few general reflections. 



Let us, says the author, cast a rapid glance upon what has 

 existed and upon what still exists in nature, in reference to 

 the Foraminifers. We have found them distributed through 

 the oolite series, extending from the lias to the uppermost 

 beds; but in the cretaceous system they appear still more 

 numerously and more varied in their forms. The Neocomian 

 beds, those of the gault and the green sand, contain many ; 

 but in proportion as we ascend from the lower to the higher 

 strata, they increase infinitely. In these latter the rock may 

 be said to be often composed of them, and, as an example, 

 we may mention the largest of the Pyramids of Egypt. In 

 the white chalk the number is nearly as great as in those seas 

 in which they now most abound. In a word, we have found 

 Foraminifers in the cretaceous basins of the Seine, the Loire, 

 the Gironde, and of the whole South of France, and in 

 Belgium. 



If we pass to the tertiary tracts, a whole world is opened 

 to us. The multiplied Foraminifers which appear in the 

 basins of Paris, Bourdeaux, Touraine, Italy, Austria, Ger- 

 many, England, and Belgium, often form there the greater 

 part of the mass. A bed of considerable thickness in the 

 environs of Gentilly, near Paris, is entirely composed of them, 

 the Foraminifers being in contact with each other, scarcely 

 united by a slight cement. In a cubical inch of the rock we 

 have ionud Jifty-eight thousand, which is equal to three thou- 

 sand millions in a metre, and shows what myriads may exist 

 in the Paris basin. These small bodies, which we thus see 

 forming entire beds in the lowest portions of the tertiary series, 

 are not less common in the higher stages; for in Austria, and 



* Memoire sur les Foraminiferes de la Craie Blanche du Basin de Parisy 

 in the 4th vol. part 1 of the Transactions of the Geological Society of 

 France, 1840. 



