OLD RED SANDSTONE OF WESTERN EUROPE. 415 
° 
Geological Society of London by Mr Turnett, were described by Dr Hooker 
as apparently belonging to two species of Calamites. At the same time Sir R. 
Mourcuison, while quoting the opinions of Dr J. FLemine and Dr TRAIL, stated 
that the sandstones from which these vegetable remains came, should, in his 
opinion, be regarded as belonging to the Upper Old Red Sandstone, and as 
overlying the Caithness flagstones.* A few years later (1858), having mean- 
while had an opportunity of personally visiting Shetland, he announced that the 
ichthyolites of the Caithness flags had not been found in Shetland, yet that 
strata of that age could now be shown to exist by the discovery at Lerwick of 
the characteristic Estheria of Thurso and Kirkwall; but he immediately adds 
that there can be little doubt that the plant-beds of Lerwick and the sandstone 
of Bressay peru hs to the younger portion of the Old Red Sand- 
stone. 
1. Geological Structure of Old Red Sandstone Area. aut the summer of 
1876 I visited Shetland with Mr B. N. Peracu, to determine if possible 
fhe connection between the Old Red Sandstone of that area and of 
Orkney and Caithness, and to ascertain whether there existed any evidence 
of contemporaneous volcanic action in the system as ‘developed at the 
northern extremity of the British Islands. We found the south-eastern 
strip of sandstone to have been laid down by Hipserr with approximate 
correctness, but to occupy on his mapa larger space and to be more continuous 
than it is in reality. A few preliminary traverses showed us that a fundamental 
| and hitherto unobserved feature in the structure of the Old Red Sandstone 
| tract of the south-east of Shetland consisted in a fault, which by bringing down 
| that formation against the older or crystalline rocks, prevents the actual base 
| of the sandstone from being reached. This fault (or perhaps a succession of 
| faults, having, however, the same general effect) begins at Rovey Head, a little 
to the north of Lerwick, and, after sweeping inland along the flanks of the 
schistose hills, turns shorewards again and reaches the coast on the south side 
of Gulber Wick. It must skirt the eastern shore a little way out to sea, for 
"where the land next projects well beyond the main coast-line at Haly Ness it 
| cuts across the head of the peninsula to Aith Voe, In the same way it traverses 
\the Sand Lodge promontory to the bay. at Hoswick. As it passes across 
the Lambhoga and Sumburgh Head region from Levenwick to Quendale Bay 
'|it dies out, and a lower series of flagstones and conglomerates is there seen to 
rest unconformably upon the metamorphic schists. All the islands lying to the 
jeast of this line—Bressay, Noss, and Mousa—consist of Old Red Sandstone. 
The largest mass of the formation, and the best sections to show the general 
succession of the beds, are to be found in the northern portion of the area. 
‘ * “Quart. Journ. Geol. Soc.” vol. ix. p. 49. 


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