TYLOR QUATERNARY GRAVELS. 



67 



Junction ; the river under the viaduct is 325 feet above the mean 

 level of the tide at Liverpool. The rails of the Taif-Yale line are 

 96 feet above the Taff at Quaker's- Yard Junction, and 30 feet at 

 Aberdare Junction, so that the rails are laid on a very steep 

 incline of 1 in 50. On the average, between B and C the fall of the 

 rail is 154 feet, and that of the river about 88 feet between the 

 two stations. The rails cross the river on a viaduct about 96 feet 

 high near the upper end of the incline, and on a bridge 30 feet high 

 at the bottom of the incline. 



Fig. 3. — Map of part of the course of the river Taff, Glamorganshire. 



^^l\ \^-W<^ 



ft. 



Bed of river Taff near Merthyr Station 4930 A. 



Bed of river at Quaker's-Yard Viaduct 297*50 B. 



Bed of river near foot of incline at Aberdare Junction. . . 230'0 C, 



Bed of river near junction of river, Clydach 199-50 D. 



Junction of river Rliondda at Pontypridd Junction 144"0 E. 



Bed of river Taff, at Taff's Well, betvreen Llantrissant 



and Walnut-tree Junction 63*0 F. 



Bed of river Taff at Pentyrch Bridge, between Walnut- 

 tree and Pen arth Junctions 490 Gr. 



Bed of river Taff at Melengriffith, between Penarth Junc- 

 tion and Llandaff Station 240 H. 



The section given in PI. lY. fig. 1 commences at Quaker's-Yard 

 Junction with a bed of loose gravel lying along the sides of the valley, 

 140 feet high above the river, but probably not of greater thickness 

 than 40 or 50 feet on any part of the rock out of which the sloping- 

 sides of the valley are excavated. The gravel is full of very large 

 boulders of the local Carboniferous rock, which is an extremely hard, 

 compact, massive -bedded sandstone of the Pennant series, several 

 hundred feet thick. These boulders are sometimes angular, and 

 sometimes weathered or rolled. There also occur quantities of Mill- 

 stone-grit, brought ten miles down the valley of the Taff, these being 

 always rolled, and boulders of limestone, with a small but conspicuous 

 percentage of well-rolled pebbles of Old Eed Sandstone from the 

 Brecon Beacons and other distant hiUs. These red pebbles are still 

 more worn and rolled than those of the Limestone and Millstone- 

 grit, the source of which is nearer to Quaker's Yard than the Old 

 Red Sandstone. The matrix is clay and sand derived from the Coal- 

 measures, or from decomposed Millstone -grit. 



After passing the ^daduct, PL lY. fig. 1, the section is continued 



1-2 



