Vol. 58. | RIVER-SYSTEM OF SOUTH WALES. DPS) 
various directions of crust-creep in the British Islands, as shown by 
the long axes of the folds and the run of the faults, he had himself 
taught for many years that they were four in number—namely, 
(1) a northerly-and-southerly, longitudinal or Malvernian ; (2) an 
easterly-and-westerly, latitudinal or Armorican ; (3) a north-easterly 
and south-westerly, diagonal or Caledonian; and (4) a north- 
westerly and south-easterly, diagonal or Charnian. These names 
were especially useful when employed as indices of direction, without 
regard to geological time. Thus the Caledonian deformation is dis- 
tinguished by a north-westerly to south-easterly creep and a 
north-easterly to south-westerly trend; the terms ‘creep’ and 
*trend’ being related one to the other much as are dip and strike. 
Folds with a Caledonian trend were as old as the Torridonian and 
as new as the Tertiary. He saw no objection, therefore, to the 
employment of the term ‘Caledonian’ for the post-Cretaceous system 
of north-easterly to south-westerly folds of the Towy and the 'Tawe. 
With regard to the Upper Severn, he had himself advocated the 
opinion that it originally formed a part of the system of the Dee, 
the gorge through the Wenlock Edge at Ironbridge having probably 
been cut in earlier Glacial times. 
It appeared to him that the Author’s suggestion that the basins 
of the Thames-Kennet and the Severn-Avon owed their original 
dividing to a low anticlinal form or ‘swell’ with a Caledonian 
trend, was worthy of serious consideration, especially as minor 
anticlines having this trend are already known along this line; 
and if the suggested synchronism of the two river-systems could 
eventually be demonstrated, a most important advance would be 
made in our knowledge of British geology. 
The AurHor replied to Prof. Groom that the terms ‘ Caledonian,’ 
‘ Armorican, etc. were used as indicative of direction only. Move- 
ments having those directions had been renewed at many different 
periods, but he was concerned only with the latest, which had con- 
trolled the river-system. He had been unable to find any clear case 
of a north-north-westerly fault crossing one of the late Caledonian 
-disturbances, except the great trough-faults described in the paper, 
and these had been dragged out of their course in the disturbed 
belt. The disturbances in Anglesey, referred to by Mr. Greenly as 
being crossed by north-north-westerly faults, no doubt belonged 
to an earlier display of movement in a Caledonian direction. The 
Pliocene beds mentioned by Mr. Salter did not share in the synclinal 
folding, and presumably were deposited after it took place. All the 
faults and fractures referred to in the paper were wholly of pre- 
Glacial age. He had had in mind a possible connection between 
the latest movements and the oceurrence of earthquakes, and 
was much interested in the remarks made by Mr. Lake on 
this subject. The Oolitic escarpment referred to by Dr. Mill, 
though so conspicuous a feature now, was wholly buried under 
Upper Cretaceous rocks when the river-system was initiated, and 
only came into relief as a result of subsequent erosion. 
