Here is a supposition of our author that corresponds to nothing which has yet been observed any where else, so far as I know. It is concerning a mineral vein, one which does not appear to differ in any respect from other mineral veins, except in being worked in that open manner which has given our author an idea of its being a valley. He then supposes that valley (or rather empty vein) to have been in this mountain when at the bottom of the sea, and that this mineral vein had then been filled with those materials which now are found in that space between the two sides of the separated rock. This is a very different operation from that of infiltration, which is commonly supposed to be the method of filling mineral veins; but, we shall soon see the reason why our author has here deserted the common hypothesis, and has adopted another to serve the occasion, without appearing to have considered how perfectly inconsistent those two suppositions are to each other. That mineral veins have been filled with matter in a fluid state, is acknowledged by every body who has either looked at a mineral vein in the earth, or in a cabinet specimen; mineralists and geologists, in general, suppose this to have been done by means of solutions and concretions, a supposition by no means warranted by appearances, which, on the contrary, in general demonstrate that the materials of those veins had been introduced in the fluid state of fusion. But here is a new idea with regard to the filling of those veins; and, I would now beg the reader's attention to the facts which follow in this interesting description, and which have suggested that idea to our author. "Quand cette matière accidentelle est enlevée, on voit la coupe du _schiste_ des deux côtes de la _fente_, faisant un _toit_ et un _mur_, parce que la _fente_ n'est pas absolument verticale: des qu'il y a un peu d'inclinaison, on distingue un _toit_ et un mur, comme j'ai l'honneur de l'expliquer à V.M. On ne connoît point encore l'étendue de ce filon, ni dans sa profondeur, où l'on ne peut pas s'enfoncer beaucoup de cette manière, ni dans la longueur, selon laquelle on continue à l'exploiter. "Voilà donc un _filon_, à la rigueur de la définition que j'en ai donné à V.M. c'est à dire, une _fente_ dans la montagne naturelle, _comblée_ de _matière_ étrangère. Mais ce qu'il y a d'extraordinaire ici, c'est que cette _matière_ vient de la _mer_: ce sont différentes _couches aquiformes_, dont quelques unes sont remplies de _corps marins_. Il y a des _couches_ d'une _terre martiale_ fort brune et sans liaison: d'autres, au contraire toujours _martiales_, sont très dures et renferment de très beau jaspe sanguin: d'autres enfin sont de vrai _marbre_ gris veinées de rouge. C'est dans ce marbre que font les _corps marins_, savoir des coquillages et des spongites; et il est lui-même martial comme tout le reste: les mineurs le nomment _Kubrimen_, et ne l'employent que comme un _fondant_ pour d'autres _minéraux de fer_.