HARDWICKE'S SCIENCE-GOSSIP. 



201 



lying the so-called ' Old Red Sandstone ' near Llan- 

 dovery, are the representatives or the Foreland beds 

 on the one hand, and of the Glengariff beds on the 

 other." Regarding thus the Lynton Sandstone (Fore- 

 land group) as Silurian, Professor Hull classifies the 

 overlying Lynton Slates and the " Middle Devonian " 

 as Devonian proper (equivalent as before-mentioned to 

 the Cornstone group) ; the Pickwell Down Sandstone 

 being regarded, together with the upper division of 

 the.Old Red Sandstone, as Old Red Sandstone proper. 

 The overlying Baggy, Marwood, and Pilton beds are 

 regarded as Lower Carboniferous, including the repre- 

 sentative of the Lower Limestone shale. 



The unconformity in Ireland between the Dingle 

 beds and the Old Red Sandstone is thus accounted 

 for by the absence of the Devonian beds. 



The following table shows the general classification 

 proposed by Professor Hull : — 



continued with little interruption since the period when 

 the Carboniferous rocks were first uplifted. The 

 waste of the rocks is shown in the Dolomitic Conglo- 

 merate and in the Lias, as well as in the blown sands 

 and alluvial muds of the present day. 



The valleys receiving many of them their first out- 

 lines in faults or fissures, and irregularities of the 

 surface, have been carved out by the agency of 

 freshwater, by streams and rivers, and by waterfalls of 

 which several well-known examples are to be seen 

 in the Vale of Neath ; and this action of freshwater 

 was no doubt modified and accelerated during the 

 vicissitudes of the Glacial period. 



One advantage of the deep valleys is the beautiful 

 scenery they afford to ramblers in search of the 

 picturesque ; * another advantage lies in the fact 

 that the coal crops out along their sides, and 

 can often be worked by adits and galleries driven 



Carboniferous 

 Old Red Sandstone 



Devonshire. South Wales and Herefordshire, &c 



Baggy, Marwood and Pilton beds 



Carboniferous Limestone and Shale. 

 Old Red Conglomerate. 



Pickwell Down Sandstones. 



IMortehoe beds 

 SSSSffl : : : : : c — tone «™p- 

 Lynton Slates J 



Silurian Lynton Sandstone (Foreland group). Ludlow rocks and Passage beds 



There is much that seems plausible in this re- 

 arrangement, and especially in the introduction of 

 Silurian beds into Devonshire. 



Professor Dewalque has hinted that the Cornstone 

 beds may be marine, and Professor Hull is disposed 

 to regard the group as the estuarine equivalent 

 of the Devonian beds, a correlation which in the 

 present state of our knowledge can only be taken as 

 suggestive. Referring to the palneontological differ- 

 ences, he observes that the discoloration of the waters 

 by peroxide of iron in the Devonian estuary of the 

 South Wales and Herefordshire district, prevented 

 the incursion of those mollusks, corals, and crinoids 

 that flourished farther south. 



That the area was a subsiding one during a long 

 period of time is proved by the successive overlapping 

 of the beds up to the Coal-measures. It is generally 

 considered that these latter were connected with the 

 Forest of Dean, and with the coal-field of Bristol 

 and Somerset ; and there seems little doubt that the 

 culm-measures of Devonshire were also connected 

 with them. The subsequent upheaval of the area 

 was attended by many undulations, whose synclinal 

 folds gave rise to the coal-basins. In South Wales, 

 the beds generally have a higher dip on the southern 

 than on the northern side of the coal-basin, while 

 numerous faults, having a north and south direction, 

 affect the Coal-measures near Swansea, testifying to 

 the disturbances that have taken place. 



The great denudations of the area have been 

 depicted by Professor Ramsay,* and they have been 



Mem. Geol. Survey, vol. i. p. 297- 



into the hills, instead of by shafts sunk from their 

 summits. 



Little has been said about the natural scenery of 

 each past period ; that, however, may be left to those 

 who conduct the geological excursions of the British 

 Association, and who amid the rocks themselves 

 may well undertake the poetic interpretation of 

 Nature. 



THE HISTORY OF THE PLANE-TREE. 



A TREE is an object which has at all periods been 

 held in a certain degree of admiration by man- 

 kind, from its grandeur, its beauty, and its use. In 

 the Scriptures there is an abundant reference to all 

 objects of nature, and its allusions to trees are pecu- 

 liarly rich. The Persians, Greeks, and Romans were 

 particularly attached to trees: some of their greatest 

 men were proud to acknowledge that they had made 

 plantations with their own hands, and fine specimens, 

 whether planted by nature or art, were held sacred or 

 specially protected. 



The extraordinary beauty of the Oriental plane 

 [Platanus orkntalis) with its massive trunk, wide- 

 spreading branches, and large handsome foliage, 

 almost tropical in appearance, giving a delightful 

 shade and coolness to the space beneath, has made it 

 in all ages an object of marked attention. This tree 

 is celebrated in the earliest record of Grecian history ; 



• See papers by Dr. Bevan, " Geologist," vol. i. pp. 49. I2 4 i 

 vol. iii. p. 90 ; and Geol. Mag. vol. ii. p. 158. 



