ROCJCS OE THE TR A PP-FORM ATION. J\$ 



to have been detached." That the pieces of fandftone are not It is denied that 



tnfulated, I have proved in a former paper. The occurrence lated or indu * 



of mafles of fandftone in veins of bafalt, grunftone, and wacken, rated. 



is well known ; but that there are mafles more indurated than 



the other fandftone of this formation, muft be deniediSas we 



know that fandftone beds occur in this formation of all degrees 



of induration. 



SedionGT. " Similar inftances of extraordinary induration p « Extraordi- 



... r . n-ii-r nary induration 



are obterved in the parts or the ftrata in contact with whinltone, f the ftraU j n 

 whether they form the (ides of the veins, or the floors and contaa with 

 roofs of the mafles into which the whinftone is diftributed. w ln on? ' 

 The ftrata, whether fandy or argillaceous, in fuch fituations are 

 ufuajiv extremely hard and confolidated ; the former in parti- 

 cular lofe their granulated texture, and are fometimes convert- 

 ed into pei feci jafper. This interefting remark was firit made 

 by Dr. Hutton, and the truth of it has been verified by a great 

 number of fubfequent observations." 



The flinty fandftone which is chara&eriftic for the neweft accounted for by 

 flotz trapp-formation, is ufually covered by clay, wacken, ba- bafeiticfolutioa 

 fait, or grunftone, in the order here mentioned : fometimes the in the pores of 

 clay is wanting, when the fandftone is covered by wacken, or "rata. 



when the wacken has been carried away, or not depofited, by 

 bafalt or grunftone. We have thus, to ufe the Huttonian lan- 

 guage, the fandftone equally indurated under a bed of clay as 

 under one of bafalt or grunftone : it is therefore plain, that no 

 argument can be drawn from the fituation and nature of this 

 fandftone in favour of the igneous fyftem. When the walls of 

 veins are indurated, we can eafily trace it to the depofition of 

 a portion of the bafaltic folution in the pores of the fofter ftrata. 



Section 68. " To the fame excellent geologift (Dr. Hutton) P. The appear- 

 we are indebted for the knowledge of an analogous fa6t attend- orc^kin^/cofl 

 ant on the paflage of whinftone veins through coal ftrata. As in the vicinity of 

 the beds of ftone where they are in contact with the veins of veins of whin, 



,. r . ,../.., . r , r r i • adduced as a 



whin, teem to acquire additional induration, lo thole or coal, in proof of their 

 like circumftances, are frequently found to have loft their fun- former fate of 

 bility, and to be reduced nearly to the ftate of coke or char- 

 coal. The exiftence of coal of this kind has been already men- 

 tioned, and has been confidered as a proof of the operation of 

 fubterraneous heat. In the inftances here referred to, that is, 

 where the charring of the coal is limited to thofe parts of the 

 ftrata which are in contact with the whin, or in its immediate 

 Vol. III. — October, 1802. I vicinity, 



