of Devonshire and Cornwall. 97 



or vice versa^ that of flint into chalk. The following reflections of 

 Saussure on this subject are strongly in point. — " These observations 

 " and these experiments appear to me to prove that the intermediate 

 " species which have been sometimes considered as forming the gra- 

 " dation from one genus to another, or as limestones partly trans- 

 " formed into flint, are very often merely mechanical mixtures of the 

 " two. In fact there is no mineral hitherto known which we might 

 " not assume as the commencement of a series, and thence proceed to 

 " establish by insensible shades a circuit comprehending the whole of 

 " those which have been already determined, and the more extensive 

 " our acquaintance with mineralogy the more will the truth of the 

 " observation become apparent, in consequence of the more nume- 

 " rous varieties and shades of difference which will be discovered."* 



It would appear however that the chalk in which flints occur, 

 although subordinate to the calcareous rocks, must, according to 

 Brongniart, belong to a formation anterior to that of the limestone 

 which he denominates grossiere. He asserts that the fossils found 

 in chalk are almost all species of extinct genera, and that the situation 

 of chalk is always inferior to that of the calcaire grossiere. f It is 

 probably this species of limestone of which the quarry of St. Eutrope, 

 near Aix in Provence consists, where the Chevalier de Sades affirms, 

 eleven beds have been formed since the existence of man in a civilized 

 state ?j: 



The western border of Dorsetshire is nearly the limit of the occur- 

 rence of flints in the chalk. This last, however, extends on the road 

 to Axminster, to within four miles of Honiton in Devonshire, where 



* Voyages aux Alpcs, § 1537. Werner, without going so far as Saussure in strictness 

 of language, is of the same opinion. NouTelieTheorie de la Formation des Filons, 55. 91. 

 + Brongniart, Elemens dc Mineralogie, tome i. p. 209. 

 X Traite de Mineralogie, par M. le Conite de Bournou, vol. ii. p. 402. 



N 



