14? MECHANICAL DEPOSITS IN MOUNTAINS, &C. 



fe£t the horizontal plane in a line from eaft to weft nearly ? 



they are very erect, thofe at Plymouth being elevated to the 

 But it is not north." That petrefactions exift in the limeftone at Plymouth 

 proved that j s ev i(fentj but that thele ftrata are primitive* ftill remain to 



tnofe ftrata are * 



primitive. be proved. The character given of the limeftone does not 



exclude it from the tranfition ftrata ; but of the fhiftus we can- 

 not judge, as neither its orydognoftical, or geognoftical cha- 

 racters are given. The other inftances which are alluded to, 

 are liable to the fame objection. I cannot therefore agree with 

 Whence the Profeilbr Playfair in believing " Though, therefore, the re- 

 eoachrtion of the ma [ ns f mar i ne animals are not frequent among the primary 

 agreed to. rocks, they are not excluded from them ; and hence the ex- 



iftence of fhell fifh and zoophytes, is clearly proved to be an- 

 terior to the formation even of thole parts of the prcfent land 

 which arc jaftly accounted the moll ancient." 

 The pofnioTT Profelfor Playfair agrees with Dr. Hutton in affirming, that 



chit vegetable vegetable matters occur in the primitive ftrata : I do not find 



matters are . ° ■ , ••,•111 



tour.d in pri- it neceflary to enter into an examination or what they have 

 naitive ftrata f^.id upon this fubject, as they have evidently confounded a 

 amined. " geognoftical with an oryclognoftical inveftigation. 

 Prof. Playfair's I fiiall now examine the proofs which Profeilbr Playfair has 

 proofs of mecha- brought to eftablifti the exiftence of mechanical depofits in 



nicil depofits in . ?. rf 



primitive ftrau primitive ftrata. 



examined. Thefirft we meet with is from Satuflure. Profefibr Playfair 



Mount St. Go- remarks, " St. Gothard is a central point, in one of the great- 

 chard a central e ft. t ra<5ts of primary mountains on the face of the earth, vet 

 primitive moun- « J . . . .... .> . J , 



cain, has arena- arenaceous ftrata are found in its vicinity, between Ayroio 



teavfftnu in anc j t h e Hofpice of St. Gothard, Sauflure found a rock, com-' 

 pofed of an arenaceous or granular pafte, including in it horn-' 

 blende and garnets. He is fomewhat unwilling to give the 

 name gres to this ftone, which Mr. KeiTon has done ; but he 

 ncverthelcfs defcribes it as having a granulated ftru&ure." 

 Ofcfervation. The rock of Ayrolo is primitive, and is either gneifs or mica' 



The rock here fl a ^ Garnets are feldom found in gneifs, but are characte- 



mentioned was ° 



picif&ormica riftic for mica flate ; the geognolt, therefore, would not hen- 

 wmu tate to conftder the rock here mentioned as belonging to mica 



flate. 

 laftances by Profeflbr Playfair continues, " Among the molt indurated 



p. Playfair of r0 cks that compofe the mountains of this ifland, many are are- 

 ceous^rinUe? 3 " naceous. Thus, on the weftern coaft of Scotland, the great 



body of high and rugged mountains on the fhores of Arafaig, 



