Scientific Intelligence — Geology. ^ 427 



of the clays and sands to tlio plastic clay of Paris, has caused them 

 to be considered as tertiary ; but their intimate alliance to metallic 

 substances, and the circumstance that none of the tertiary fossils have 

 hitherto been found either in the district of Condros, or in the other 

 elevated localities of the massive anthracite (du massif anthraxifere) 

 are, in the apprehension of M. d'Omalius, so many reasons which in- 

 cline him to separate them entirely from the tertiary series of rocks. 

 According to him, these sands, clays, and mineral ores have followed 

 hard upon the formation of the coal measures, and have come to light 

 during their contortion (sent arrives au jour lors du plissement). As 

 to their mode of formation, M. d'Omalius believes, that if, instead of 

 deriving these sands and clays from superficial waters, we were to 

 suppose they proceeded from the interior, like metallic veins, and as 

 M. d'Alberti supposes with respect to triasic sands and sandstones 

 (les gres et les sables triasiques) their position would bo explained 

 with the greatest facility. The volatilisation of silica does not ap- 

 pear to him of more difficult supposition than that of magnesia, which 

 is admitted by many geologists. Accordingly, he remarks, it may 

 easily be conceived that if siliceous gas traversed masses of waters, 

 it might produce chemical reactions which would precipitate silex, 

 either in a pure state, or in that of silicates of alumina, or, to put it in 

 other terms, which might produce sands and clays, in the same way 

 as the waters of certain existing fountains precipitate carbonized lime, 

 because the carbonic acid which held this salt in solution is precipi- 

 tated when the water comes to the surface. 



M. d'Omalius designates by the term phtanite the whole of that 

 substance which the inhabitants of the Condros district call clavia, 

 although it is only a portion of these matters which belong to that 

 modification of quartz to which Ilaiiy has given the appellation of 

 phtanitey and though they present numerous varieties, in passing from 

 phtanite to grey jasper, to red jasper, to hornstone, millstone, flint, 

 (pyromaque), quartz, sandstone psammite, loam (Hmonite), to red 

 iron-ore, schist, ampelite, &c. The relations of the phtanites with 

 the minerals of iron, also with the clays and sands, induce M. d'Oma- 

 lius to think that they have the same origin, to this extent at least, 

 that they proceed alike from internal emanations ; but their state of 

 cohesion leads to the belief that they are not the result of instantane- 

 ous precipitations, which are supposed to occur in the case of clays 

 and sands, but that they must, on the contrary, proceed from mole- 

 cules which preserve their state of solution till they arrive at the sur- 

 face, and then unite after the common laws of affinity. — L'Institut, 

 No. 397. 



5. QeognosUc Pogition of the i>ia«K>«d— Tho Brussels Academy 



