Notices of Memoirs — Frof. T. Rupert Jones. 371 



iTOTioiES OIF nycEnvcoiias. 



I. — On the Primeval Eiveks of Bkitain.' 



By T. EtrPERT Jones, F.G.S., Professor of Geology, etc., Royal MiKtary College, 



Sandhurst. 



THE geological action and results of rain and rivers may be easily- 

 recognized by even casual observers. The muddy waters of a 

 clay country after showers, and the numerous little deltas of rain- 

 washed grit and mud on the slopes of roads and fields where sandy 

 soil abounds, attest the action of the rain in removing earthy material 

 from a higher to a lower level, under ordinary circumstances. The 

 powerful action of torrents suddenly charged with melted snow or 

 with tropical rains^ or locally flooded by a bursting water-spout, is 

 well known, and can be likened only to the devastating agency of a 

 broken reservoir, such as those of Huddersfield and Sheffield. In 

 all cases mud, sand, and shingle, together with drifted timber, herbage, 

 leaves, and water-plants, bones and carcases, insects, shells of land 

 and water molluscs, and other organic remnants, are slowly or sud- 

 denly moved down-stream, — laid down here, stirred up and pushed 

 forward there, — buried deeply at one place, ceaselessly drifted to and 

 fro at another ; and such changes go on until the river-plain, having 

 been made level by marsh-deposits, and excavated repeatedly along 

 the wandering lines of the river's changing course, extends seaward ; 

 and the delta pushes out even into the sea, which takes more and more 

 of the mingled detritus for its share, laying it down in the deeps and 

 the shallows with a seemingly capricious irregularity, which is, really, 

 recognizable order, dependent on the gravity of particles and the 

 force and direction of tides and currents. 



By its alluvium, or deposits of gravel, sand, and mud, often black- 

 ened with peat or charged with shells and bones, the river keeps an im- 

 perfect record of its work, as a carrying agent, in removing the ruins 

 of the higher ground, whether reduced by the chipping frost and the 

 grinding glacier, by the soaking mists and sapping springs, by the 

 washing rain and raging torrents, .or by all of these, assisted by the 

 slow and sure decomposing power of carbonic acid. As a red river 

 runs from red ground, so does a muddy river come from clay ground, 

 and a hard-water river from limestones. The shingle of slate or 

 quartz-rock, of granite or mica-schist, of sandstone or limestone, bears 

 direct evidence of its local origin ; and the sand from old sandstones, 

 from the quartz of granite newly rotted, or from the frost-bitten 

 quartz-rock, still shows traces of its birth-place. Whether in lakes 

 or seas, such detritus tells of its former belongings, and is subject to 

 unchangeable laws of deposition and arrangement. Clay may have 

 been fine mud derived directly from the decomposition and degrada- 

 tion of felspathic rocks, or from the wear and tear of clay-slates, 

 shales, and other argillaceous rocks ; but in any case the river carries 



1 Being the substance of a lecture given at Southerndown, July 20th, 1869. 

 Reprinted from the Proceedings of the Cardiff Naturalist's Society. 



