THE LAURENTIAN EOCKS. 



13 



witli great beds of triclinic felspar^ 

 especially of tliat peculiar variety 

 known as labradorite, or Labrador 

 felspar, and wMch sometimes by its 

 wonderful iridescent play of colours 

 becomes a beautiful ornamental 

 stone. 



I cannot describe sucb rocks, 

 but tbeir names will tell something 

 to tkose wbo bave any knowledge 

 of tbe older crystalline materials 

 of tbe eartb^s crust. To tbose wbo 

 bave not, I would advise a visit 

 to some cliff on tlie lower St. Law- 

 rence, or tbe Hebridean coasts, or 

 tbe sbore of Norway, wbere tbe 

 old bard crystalline and gnarled 

 beds present tbeir sbarp edges to 

 tbe ever raging sea, and sbow tbeir 

 endless alternations of various kinds 

 and colours of strata often diversi- 

 fied witb veins and nests of crystal- 

 line minerals. He wbo bas seen 

 and studied sucb a section of Lau- 

 rentian rock cannot forget it. 



All tbe constituents of tbe Lau- 

 rentian series are in tbat state 

 known to geologists as metamor- 

 pbic. Tbey were once sandstones, 

 clays, and limestones, sucb as 



pq 



CQ 



OQ 



tZ2 



i p5 



K] 



:si 



a. 



■^ 1=1 

 bJD 



ft . 



^Ci5 



