240 REPORT OF MEETINGS FOR 1902 



on a grain of sand. The result has been to redevelop a 

 crystalline outline on grains of quartz which, perhaps, had 

 the very same form before it was worn oflF by prolonged 

 attrition. The remarkable feature about the secondary quartz 

 is the fact that in many cases the new quartz is deposited 

 upon the old in exact accordance with the molecular structure 

 of the original. As Professor Judd has pointed out in referring 

 to this interesting fact, the crystalline materials seem to 

 possess what one is almost tempted to call a certain amount 

 of vitality, so far as reparative powers are concerned. And 

 it matters not how long a time elapses between an injury to 

 a crystal, resulting in the obliteration of its proper form, 

 and the time when that form is again developed. Half the 

 events in the geological history of the Earth may have happened 

 in the interval, and yet the process is completed just as 

 perfectly as at first. We owe it mainly to the researches 

 of Mr Sorby that our attention has been called to these 

 points. Some of his first studied specimens came from the 

 locality where the leader of the party described the facts. 



Near the top of the Upper Old Red Sandstone there usually 

 occurs a record of a change in the olimatal conditions 

 that set in about the time when this section of the rock was 

 formed. It usually consists of a sandstone, less brightly 

 coloured than that below, and full of nodules, flakes, and 

 concretions, of calcareous matter. These are the Cornstones. 



In those districts where the succession from the Old Red 

 to the Carboniferous is complete, there is usually a considerable 

 thickness of shales and clays containing nudules and bands 

 of impure argillaceous limestone. These beds are the Ballagan 

 Beds, otherwise known as the Cement Stones, or as the Lower 

 Tuedian. They are the Scottish representatives of what have 

 long been called in other parts of the kingdom the Lower 

 Limestone Shales. They are of great thickness in the Tweed 

 Valley, and also in the Border country to the west. Around 

 Edinburgh they are fully twelve hundred feet in thickness, 

 and the volcanic rocks of Arthur Seat and the Calton Hill occur 

 in their middle part. But they are locally absent in Fife, 

 where the Oil Shale series lies directly upon the Upper Old 

 Red owing to deposition having taken place there against 

 a sloping bank, consisting of the Upper Old Red Sandstone. 



