Correspondence. 521 



the alluviums have been cut through, and are vanishing in the form 

 of parallel terraces and " Karnes." There are ancient terraces and 

 alluviums recent and in actual formation, in the long and beautiful 

 gorges of the Lower Mouse-water wherever an interval of soft 

 strata occurs in the banks of these gorges. One may be seen from 

 the road and bridge immediately above the magnificent gorge 

 through Cai-tland Crags. Another immediately above the almost 

 equally magnificent gorge, beginning at Cleghom bridge. Man has 

 run his roads and bridged the river at these two crossing places of 

 nature. Below Cartland Crags vast alluviums have always (that is, 

 for millions of years) existed above Stonehyi'es Fall, caused by the 

 hardness of the rocks there. The remains of these alluviums are still 

 to be seen on the hill side, and modern ones are still growing from 

 the same cause. Indeed, the singularly hard Devonian conglomerate 

 rocks at Stonebyres Fall still give the level to the bed of the Mouse- 

 water through Cartland Crags. Every one (except Mr, Mackiutosh) 

 will allow that the Mouse-water has cut the gorge through Cartland 

 Crags backward, and that it must once have run at a level as high as 

 the top of these Crags. Who shall say how much higher these rocks 

 have been ? though we scarcely need them higher than they are to 

 account for all the alluviums behind them. The Clyde becomes 

 smooth and sluggish about TuUyford, above Bennington, with new 

 alluviums, and the banks are terraced with old alluviums of sand, 

 with pebbles. While, where the railroad from Lanark to Douglas 

 crosses the river, the country is one wide sea of ancient terraced 

 alluviums. These extend over the hills between Lanark (by Eavens- 

 truther) and Carstairs. So that the water-parting between the Clyde 

 and the Mouse-water is formed by hills capped with these alluviums. 

 The Clyde, from Carstairs up to its source, is at the same work now, 

 which it has been at for millions of years. That is, it is still cutting- 

 through old and recent alluviums, or " haughs," of all ages and at 

 all levels, and forming new ones, which it gives, as Aladdin did his 

 lamps, in exchange for old ones. This may be seen from the railway 

 at express pace. Mr. Geikie seems wantonly to introduce " mystery" 

 and marvel where in nature simplicity itself reigns. He turns a 

 certain pool into the crater of a volcano, like one of those in the 

 Eifel. Now the bed of this volcanic pool is formed of the most 

 perfectly ivater-worn pebbles, and its sides of drifted sand, boulders, 

 and pebbles — most remarkable materials for the construction of a 

 volcanic crater ! Yours, &c., &c. 



GEOKaE Greenwood, Colonel. 

 Bkookwood Pare., Alresforb, 

 5th September, 1866. 



P.S. 17th October, — In the Geological Magazine of this month, 

 page 435, Mr. Topley applies the rain and river theory most 

 admirably to the northern half of the alluvial streams which unite at 

 the Humber gorge, as he formerly did to those which unite at the 

 Medway gorge through the North Downs. But the principle at the 

 beginning of this paper applies equally to the Trent and to all the 

 southern and western streams which flow from the Pennine chain 



