162 Professor Keilhau on 



these geologists so strongly profess to adhere is directly 

 violated by themselves. The notion that a solidification 

 under strong pressure, or great tension, and so forth, might 

 possibly have produced the peculiar texture in these rocks, 

 should least of all have been heard from those theorists at 

 whom we are now aiming, who, according to their own ac- 

 count, follow such strict principles. But it is still worse 

 that this party must deny the very clearest geognostical facts, 

 in order to maintain their opinion. It has now been ob- 

 served in many places, that strata of rock, which can be re- 

 cognised by any one, by means of the usual characters, as 

 masses that have been produced in the mechanical way, and 

 deposited in water, present themselves for a longer or shorter 

 portion of their extent as gneiss, mica-slate, or some one of 

 the rocks now under discussion, and thus plainly exhibit a 

 transmutation in these portions, inasmuch as a direct " Nep- 

 tunian " crystallization can just as little be supposed here as 

 in other cases. As here the geognostical fact itself decides 

 the question in dispute in the most complete manner, inas- 

 much as the confirmation of these geognostical observations 

 gives it to us as a pure result of observation^ as 2ifact, that se- 

 dimentary, originally uncrystalline masses, have, at certain 

 points, been converted into gneiss, mica-slate, &c., it must be 

 flatly denied by the just mentioned party that such strata exist, 

 which are partly crystalline silicide masses, but in their other 

 portions have retained that condition which betrays the ori- 

 ginal formation of the whole by means of deposition in water ; 

 and, accordingly, this mode of proceeding has not been omitted. 

 The opponents of the principle of transmutation have a 

 much better field in regard to conversions that have taken 

 place on the great scale. Where we see no unaltered remains 

 of the transmuted masses, the conviction of the change that 

 has occurred does not follow directly from the geognostical 

 phenomena themselves, but can only be founded on the con- 

 clusions derived from other evident cases. As in this way the 

 knowledge was obtained that entire large countries, which are 

 almost entirely composed of gneiss and similar rocks, are 

 enormous altered formations of sandstone, clay-slate, &c., this 

 result did not fail to be termed an hypothesis ; and under this 



