Welsh Gallery

Geological map of the British Isles

Geological map of the British Isles, with a colour-coded key (right, see C015/2656 for details and names). The geology of the British Isles is extremely varied with rocks from nearly all geological periods. The rock formation types shown are: sedimentary, metamorphic and igneous. The majority of the rocks in Ireland, England and Wales are sedimentary, with large areas of volcanic and metamorphic rocks in Scotland. The sedimentary rocks are colour-coded by geological period from most recent to most ancient (top to bottom). The oldest rocks are in north-west Scotland, the youngest in south-east England. For a simpler map with less detail, see C015/2655.

© GARY HINCKS/SCIENCE PHOTO LIBRARY

Machynlleth, town clock

The clock is a landmark in the centre of Machynlleth. It was built by the residents of Machynlleth to celebrate the coming of age of the eldest son of the Fifth Marquess of Londonderry, who lived at Y Plas. Charles Stewart Vane-Tempest (Viscount Castlereagh) turned 21 on 16 July 1873, but family bereavement put paid to the planned celebrations. A year later, on 16 July 1874, the clock's foundation stone was laid amid general festivities.

© David Williams

First geological map of Britain, 1815

First geological map of Britain, detail of the north east coast (figure 8). This map was published in 1815 by British geologist William Smith (1769-1839). It shows rock layers (strata) in England and Wales and part of Scotland (key at lower left). Smith's work as a canal surveyor allowed him to study geology. He discovered that geological strata could be reliably identified at different places on the basis of the fossils they contained. Smith also proposed the principle of superposition, that if a strata overlays another then it was laid down at a later time. He is considered the father of English geology.

© NATURAL HISTORY MUSEUM, LONDON/SCIENCE PHOTO LIBRARY