MODE XII. SLA.TB. 115 



the same ; and of which the inclination is also 

 seventy degrees, but in an opposite sense, so that 

 when they meet the former they either form 

 rhombs, or half rhombs, which Guettard com- 

 pares to the letter V; some being upright, while 

 others are reversed. 



" All the layers or leaves of the slate have a 

 direction and inclination similar to those of the 

 first veins of quartz; that is to say, that they 

 rise seventy degrees towards the south, and dip 

 towards the north : and even when intersected 

 by veins which have an opposite inclination, 

 theirs is not changed. The whole mass is thus 

 divided into immense rhomboids, composed of 

 plates all parallel amongst themselves, and with 

 the two opposite faces of the rhomboid. 



" The slate of Angers is extracted in blocks 

 of a fixed size, which are divided, as at Charle- 

 ville, into repartons and leaves. It is betwixt 

 these leaves that there are frequently found ves- 

 tiges of marine animals, and above all pyritous 

 impressions of pous-de-mer (the sea-louse, a little 

 univalve shell of the courie kind) ; of little che- 

 vrettes (shrimps or prawns); and a kind of crab, 

 of which the body is about a foot in breadth, 

 and fourteen or fifteen inches in length, the tail 

 having nine or ten rings. The shrimps are 

 sometimes so numerous, that Guettard counted 



