238 REPORT OF MEETINGS FOR 1902 



But when a geologist asks men of science, who do not 

 happen to be cognizant of the facts with which his own studies 

 make him familiar, to accept his statement that the Earth 

 is much older than they have been accustomed to think, 

 they turn aside with a smile, and ignore his remarks, as 

 the men of old did those of the astronomers. We, too, can 

 smile, and wait. 



(III.) The Rock3 on the Shore between the Siccar Point 

 AND Cove. 



After returning to the top of the cliff, the party wended 

 their way northward for some distance, and then descended 

 to the shore to examine the higher members of the Upper 

 Old Red Sandstone. These are (as it happens) both sandstones, 

 and of a red colour. The red colouring matter is due to 

 the presence of a film of red oxide of iron — probably the 

 mineral Turgite, though in some cases it may be the pure 

 anhydrous ferric oxide Hasmatite. The iron coats the surface 

 of the grains of sand. It has been shown by Mr Hudleston 

 and others (including the present writer*) to be due to the 

 formation of these rocks under conditions of aridity, when 

 little or no organic matter found its way into the few shallow 

 saline lakes or Schatts in which part of the Upper Old Red 

 Sandstone of this part was formed. Many of the sandstones 

 are composed of well rounded grains of sand, identical in 

 character with the desert sands of to-day, and, like them, 

 showing the rounded form and polished surface which they 

 have acquired through prolonged drifting by the action of 

 the wind. Part of the Upper Old Red here may be confidently 

 referred to an origin similar to that of the sand hills of the 

 modern deserts. 



Some of the grains of sand show beautiful examples of 

 what is called "secondary quartz." Weak solutions of silica 

 have percolated through the rocks, and the silica has thus 

 been redeposited almost wherever it encountered a clean surface 



* See "Desert Conditions in Great Britain." — Trans. Edin. Geol. Soc, 

 Vol. VII., pp. 203-222. 



