This naturalist had discovered along the side of the Rhine many ancient volcanos which have been long extinct; but that is no part of the subject which we now inquire after; we want to see the operations of subterraneous lava which this author has actually exposed to our view without having seen it in that light himself.  He would persuade us, as he has done himself, that there had been in the ancient sea volcanic eruptions under water which formed basaltic rocks; and that those eruptions had been afterwards covered with strata formed by the deposits made in that sea; which strata are now found in the natural position in which they had been formed, the sea having retreated into the bowels of the earth, and left those calcareous and arenaceous strata, with the volcanic productions upon which they had been deposited, in the atmosphere.

It would be out of place here to examine the explanation which this author has given with regard to the consolidation of those deposited strata which is by means of the filtration of water, but as in this place there occurs some unusual or curious examples of a particular consolidation of limestone or calcareous deposits, as well as similar consolidations of the siliceous sort, it may be worth while to mention them in their place that so we may see the connection of those things, and give all the means of information which the extremely attentive observations of this naturalist has furnished to the world of letters.

At Oberwinter our author remarks a stratum of consolidated sand above volcanic matter, Tome 4, p. 162.  “Tant que j’ai parcouru le pied du cone, je n’ai vu qu’un terrain compose de ces debris, et cultive en vignes.  Mais apres l’avoir depasse, j’ai trouve la coupe verticale d’une colline a couches pierreuses, si reguliers, que je les ai prises au premier coup d’oeil pour de la pierre a chaux.  L’esprit de nitre m’a detrompe:  c’est une pierre sableuse tres compacte, dont les couches, qui n’ont souvent que quelques pouces d’epaisseur, s’elevent par une pente insensible vers le cone volcanique qu’elle recouvrent de ce cote la sans aucune apparence de desordre.  Ces couches qui sont visiblement des depots de la mer, quoique je n’y ai pas trouve de corps marins, ont ete formees depuis que le cone s’etoit eleve.”

This is a species of reasoning which this acute naturalist would surely not have let pass in any other cosmologist.  But here the love of system, or a particular theory, seems to have warped his judgment.  For, had our author been treating of beds or bodies deposited in water, and preserving the natural situation in which they had been formed, he would have had reason to conclude that the superior bed was of the latest formation; but here is no question of superincumbent strata; it is a stratum which is superincumbent on a lava; and it is equally natural to suppose the lava posterior to the stratum as the stratum posterior to the lava.