1873.] 



JtTDD THE SECONDARY ROCKS OP SCOTLAND. 



133 



"3 ^o-S 



a 2 SP^-Mfq 



Since my return to England, my 



obscurely, in the gorges cut 

 through the drifts by the 

 Easter and Wester Garty 

 Burns and the Lothbeg 

 river *. 



Here then we have proof 

 that the great fault which 

 has brought about the juxta- 

 position of the Primary and 

 Secondary strata in Suther- 

 land has, through about five 

 miles of its course, become 

 double, the strata on the 

 south-east having been let 

 down by two steps instead 

 of one ; and thus a strip of 

 an intermediate formation 

 has been preserved. Similar 

 phenomena, on a smaller 

 scale, are familiar to all 

 field-geologists who have 

 mapped greatly faulted dis- 

 tricts. 



We have thus shown that 

 the preservation of the in- 

 teresting patches of Secon- 

 dary strata in the north-east 

 of Scotland is entirely due to 

 the concurrence of a series of 

 favourable accidents. First 

 among these (both in order of 

 time and in importance) we 

 must rank those great dislo- 

 cations which have brought 

 the strata in question into 

 apposition with rocks of so 

 much greater hardness and 

 capability of resisting de- 

 nuding forces. The general 

 strike of these great faults 

 is from N.E. to S.W. ; and 

 they doubtless constitute a 

 portion of the results of that 

 great and long-continued 

 series of disturbances which 

 have so largely contributed 

 to the production of the phy- 

 sical features of this island. 

 The influence of this great 

 indefatigable friend Mr. Joass informs 



