STRATA IN THE NKIGHBOURIIOOD OF LONDON. ^Q 



nation should be connerted with that of the several strata, 

 in which they are found*. 



Already have these examinations, thus carried on, taught General facts, 

 us the followins^ highly instructive facts. That exactly 

 similar fossds are found in distant parts of the same stratum, 

 not only where it traverses this island, but where it appears 

 a«;ain on the opposite coast: lh:\t, in strata of considerable 

 comparative depth, fossils are found, which are not disco- 

 vered in any of the superincumlient beds : that some fossils, 

 which abound in the lower, are fcAind in diminishing numbers 

 throui^h several of the superincumbent, and are entirely 

 wanting in the uppermost strata: that some fossils, occur- 

 ring in considerable numbers in one stratum, become ver}' 

 rare in the adjacent portion of the next superincumbent 

 stratum, and afterward are lost: that fossils of one particu- 

 lar genus, which exist abundantly in the lower strata, and 

 occur in several of the superincumbent ones, are not found 

 in the three highest strata ; while one species of that ge/ius, 

 but which has not been found in a fossil state, exists in our 

 present seas : and lastly, that most of the remains, which 

 are abundant in the superior strata, are not at all found in 

 the lower. These general facts lead us to hope, that 



♦ This mode of conducting our inquiries was long since recommended 

 by Mr. W. Smitli, who first noticed, that certain fossUn are peculiar to 

 and are onlj/ found lodged in particular slirala ; and who first ascertained 

 the constancy in the order of' superposition, and the continuity of the strata 

 qf this island. It will appear from the following quotation, that tliese 

 observations have lately aU^o occurred to Messrs. Cuvier and Brongniart, 

 while examining into the nature of the strata of the neighbourhood of ^ 



Paris. '* CetteconstaDce dans I'ordre do superposition des couches les 

 ** plus minces, et sur une etendue de 12 myrianietres au moins, esr, 

 ♦' selon nous, un des fails les plus remarquables que nous ayons constates 

 " dans la suite de n«s recherchcs. If doit en resulter pour les arts et 

 " pour la gtologie des consequences d'autant plus interessantes, qu'elles 

 " sont plus sAres. 



*• Le moyen que nous avons employe pour reconnoitre au milieu d'un 

 " si grand nombre de lits calcair<;s, un lit deji observe dans un canton 

 *' trcs-eloigne, est pris de la nature des fossiles renferm6s dans chaque 

 " couche, ces fossiles sont toujours generalement les memes dans les 

 •* couches correspondantes, et presentent des differences d'esp^ces assez 

 " notables d'un sysleme des couches i un autre syst^me. C'est un signe 

 " de reconnoissance quijusqu'a present ne nous a pas trompes." An- 

 nale.=; du Museum d'histoire naturelle, tome XI, p. 307. 



geology 



