360 Prof. Keilhau on the Formation of 



likewise forms isolated masses in its hanging and lying includ- 

 ing strata ; the limestone in this instance being usually in very 

 thin stripes between the strata, and the portions of slate like- 

 wise being parallel to the planes of stratification of the great 

 slate masses. The individual plates of mica, too, which occur in 

 the manner just stated in the marble near its junction, are 

 parallel to the planes of stratification ; and the same is the 

 case with the hornblende crystals which are met with in the 

 marble, when the latter is in contact with hornblende -slate. 

 All this plainly shews that, in fact, no such entirely exclu- 

 sive process of formation can have produced such a marble ; 

 whereas it is clear that the origin of the marble and that of 

 the slate, both as regards the time and the mode of produc- 

 tion, have had very much in common with each other. If now 

 we must, in so far as the slates compose! of siliceous com- 

 pounds are concerned, reject the Neptunian theory (and this 

 I regard as absolutely necessary), this must also be done in 

 reference to the marble.* And those who are of opinion that 

 the calc-spar constituting the marble has been formed by car- 

 bonate of lime in a state of fusion, or, at least, softened by 

 heat, having been slowly solidified under sufficient pressure, 

 will, in consequence of the above-mentioned relations of the 

 whole mineral combination, doubtless not fail to admit that 

 the silicates and the quartz of the slate are equally the pro- 

 ducts of fusion ; while, on the other side, it will be conceded, 

 that if the non-pyrogenic origin of the including slate can be 

 proved, a pyrogenic origin cannot be assigned to the marble. 

 This result will, I hope, be kept in remembrance afterwards, 

 when we consider the origin of the primitive slates. Those 

 who already, perhaps, think that this marble has been formed 

 by *' actions lentes^'' without heat, will doubtless refer to the 

 analogy of its geognostical relations with those of the masses 

 of marble occurring between uncrystalline strata, which were 

 already discussed. 



With respect to the crystalline limestone, an esteemed 



• I shall not pause here to adduce arguments against the Neptunian hypothe- 

 sis. The many silicates occurring in primitive limestone contradict it, as was 

 shewn by Berzelius in his Jahreshericht for 1839. • 



