348 



ILLUSTRATIONS OF THE 



part of the whole : but the proportion of it occu- 

 pied by granite cannot at prefent be afcertained 



exadlnef 



r 



lodft fhall fi 



fu 



will, till feme 

 to examine th 



mniera< 

 courfes 



f the great rivers, the Dee, the Spey, & 



^erfe this coun: 

 the whole furfa 



y. 1[ we call it one- fourth 



\ 



e, its extent is certainly not 



der- rated, and will amount to 790 fq 



y ; to wh 



dding 150, as a very full 



lowance 

 Scotland 



F 



for all the other g 



C 



d 



3^3 



exclulive of the ifles, we (liall have 

 940 fquare miles, between a twenty-fourth and 

 twenty-fifth part of the furface of the whole. 



This computation, it mult be obferved, aims 

 at nothing precife, but I think it. is fuch, that a 

 more accurate furvey would rather diminifh than 

 increafe the proportion affigned in it to the gra- 

 nite rock. 



V 



This refult miay perhaps fall as much 

 iliort of Mr Kirw^an's notion, as it exceeds the 

 ellimate made by Dr Hutton. If it fhall not, and 

 if the former has, in this inftance, come nearefl 

 the truth, it cannot be afcribed to the accuracy 

 of his information, or the foundnefs of the prin- 

 ciples which directed his refearch. Mr Wil- 

 liams, whom he quotes, was a miner, of great 

 Ikill and experience in fome branches of his 

 profeffion, to which, if he had confined him- 



felf, he might have written a book full of ufe- 



ful 



