AND THEIR MEETING WITH GRANITE. 10*7 



from one side of the island to the other, seems to be uniform 

 throughout, except in the immediate neighbourhood, or con- 

 tact of the granite, where it assumes a micaceous character, 

 approaching to the nature of gneiss or mica-slate. This fur- 

 nishes a most notable indication of the action of heat ; since 

 the granite, by its local intensity, has performed the very ef- 

 fect which Dr Hutton ascribes to the general heat below, 

 as acting upon the lower beds, and converting them into 

 gneiss. 



Another circumstance of importance is, that at the Rae 

 Quarry in Peeblesshire, nearly in the middle of this mass of 

 killas or grauwacke, a bed of limestone occurs, interstratified 

 with the killas, and of course coeval with it, which bed con- 

 tains shells in abundance. Now, as this mass of killas has 

 been proved to be of older formation than the granite of Gal- 

 loway, it is obvious that granite is here found to be of a for- 

 mation posterior to the existence of living animals. 



The relative age of granite and of sandstone has not been 

 decided in any case that I have had occasion to observe, and 

 is a point of considerable importance in geology. Nothing 

 seems as yet to prove, that granite may not have flowed up 

 against a stratified mass, possessing, in some of its parts, the 

 properties of sandstone ; I conceive, however, that these pro- 

 perties will nowhere be found to belong to that part of the 

 stratified mass which lies close to the granite. For we have 

 seen, on the Lauren, that killas near the junction has been 

 changed into gneiss or mica-slate by the heat of the granite, 

 as we conceive ; and there is still stronger reason for believing, 

 that a similar change would take place on sandstone in the 

 same circumstances. We ought, therefore, to find, that while 

 a remote portion of the stratified mass retains the properties 

 of sandstone, that which lies but at a little distance from the 



O 2 granite, 



