106 DOMAIN IX. ANOMALOUS, 



the precise epoch of their creation; and thus a 

 few shells might appear even in substances styled 

 primary. 



eb g b"es f That patient and careful observer, Saussure*, 

 has established as an axiom, that pebbles ori- 

 ginally so formed, and not produced by attrition, 

 may be distinguished by their concentric layers, 

 or by a nodule, whose form corresponds with 

 that of the stone : thus what he calls petrosilex d 

 ^corce, or with a rind, is a flint found in natural 

 nodules, the rind being from six lines to an inch 

 in thickness, of a grey almost opake; whilst the 

 concentric kernel is of a fawn-colour, and semi- 

 transparentf. 



With regard to rolled pebbles, the study of 

 which he has particularly recommended, as per- 

 haps more essential to the theory of the earth 

 than that of the rocks themselves, Saussure has 

 remarked, and the observation has since been 

 repeatedly confirmed, that the pebbles of the 

 vales among mountains are derived from the 

 rocks of which these mountains consist; but the 

 pebbles of the large open plains seem as if 

 dropped from the sky, no parent rocks appearing 

 in a space of hundreds, and even of thousands 

 of milesf. It would seem, from many circum- 



