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The Pamphlet Collection of Sir Robert Stout: Volume 22

II. Previous Literature on the Subject

II. Previous Literature on the Subject.

The boulder clay of Caithness has long been celebrated for the abundance of organic remains which are present in that deposit, and its origin has consequently given rise to considerable discussion. The occurrence of marine shells in the boulder clay was first made known by Hugh Miller in the pages of The Witness in 1847, where he states that Mr John Cleghorn of Wick and Mr Dick of Thurso had supplied him with shells from their respective sides of the county.* The writer of the article also states that, to Mr Dick's chagrin, he had come across an old work, entitled, "Minutes of Observations Drawn Up in the Course of a Mineralogical Survey of the County of Caithness in 1802 by John Busby, Edinburgh," wherein were chronicled several instances of the occurrence of marine shells in the blue clay of Caithness. The survey was made at the instance of Sir John Sinclair.

In his rambles across the county Mr Dick brought to light many localities where this deposit yields marine shells, and blocks of fossiliferous secondary rocks along with chalk flints. He detected the ice-markings on the rocks at Thurso, and he noted the occurrence of erratics at various points which had travelled far from their parent sources. Indeed, his long-continued examinations of the sections from the Thurso river to Freswick burn and southwards to Dunbeath, led him to the belief that the boulder clay, in some way or other, was of glacial origin.

* "Rambles of a Geologist; or, Ten Thousand Miles over the Fossiliferous Deposits of Scotland."

See "Life of Robert Dick," by Smiles, pp. 159, 164, 169, 184, 187, 195, 223, etc.

page 5

To Mr C. W. Peach, however, geologists are indebted for most of the knowledge we possess regarding the organic remains of that deposit. His residence at Wick for many years afforded him frequent opportunities of making collections of these remains. The results of his observations have been communicated mainly to this Society, and have been published in the Transactions, while some reports were also presented to the Geological Section of the British Association.* He was the first to publish lists of the organic remains, and was likewise the first to recognise the resemblance between the ice-worn blocks of the secondary rocks in the boulder clay and the representatives of these rocks on the Sutherlandshire coast. In 1868 he informed Dr Croll that his researches had led him to the conclusion that the boulder clay was a genuine product of land ice, and in every respect identical with Scotch till. He also stated that he had come to believe that the ice movement had been from the Moray Firth towards the Atlantic, and that in all likelihood it might have been produced by masses of land ice crossing the Moray Firth from the high grounds to the south-east.

In 1866 Mr T. Jamieson, in a paper on "the Glacial Phenomena of Caithness," gave an excellent account of the shelly boulder clay, referring specially to its distribution, its physical characters, and organic remains. He advocated the theory that this deposit was due to floating ice during what he terms the glacial marine period, and he suggested that the transport had been from the north-west to the south-east, across the country between Reay and Dunbeath. The main argument adduced by him in support of this movement from the north-west, is the overlapping of the dark grey shelly

* See the following papers by Sir. C. W. Peach in the Trans, of the Roy. Phys. Soc., Edin., "On the Discovery of Calcareous Zoophytes in the Boulder Clay of Caithness," vol. i., p. 18; "On the Discovery of Nulliporcs and Sponges in the Boulder Clay of Caithness," vol. ii., p. 98; "On the Fossils of the Boulder Clay of Caithness," vol. iii., p. 38; "Further Observations on the Boulder Clay of Caithness, with an Additional List of Fossils," vol. iii., p. 396; also Brit. Ass. Rep. for 1862, Trans, of Geol. Sec., p. 83; Ibid, for 1864, p. 61.

Geol. Mag., 1870, p. 212.

Quart. Jour. Geol. Soc., vol. xxii., p. 261.

page 6 drift on the grits and conglomerates towards Dunbeath and Berriedale, coupled with the overlap of a reddish-brown boulder clay on the Caithness flags at Reay. We shall point out presently, however, that these features are satisfactorily accounted for by supposing that the ice came from the southeast. We shall have occasion to point out also that this supposed movement from the north-west is at variance with some facts recently brought to light regarding the direction of the ice-markings and the dispersal of the stones in the boulder clay, while it leaves unexplained the occurrence of various secondary rocks in that deposit. Mr Jamieson inferred that the shelly boulder clay of Caithness was of more recent date than the lower boulder clay of Scotland, which is usually unfossiliferous, being led to this conclusion by the small proportion of Arctic forms in the fauna of that deposit.
In 1870, our colleague, Dr Croll, contributed an article to the Geological Magazine,* in which he disputed the marine origin of the Caithness boulder clay, regarding it as a product of land ice. He called attention to two points noted by previous writers on the subject: first, that with the exception of the organic remains, this deposit closely resembles the ordinary boulder clay of Scotland, which is generally ascribed to the action of land ice; and, second, that the marine shells are scattered irregularly through the deposit, and are smoothed and striated precisely like the stones in the boulder clay. He argued that the presence of these organic remains does not necessarily prove the marine origin of the till, but rather that they had been borne inland with the moraine profonde from the bed of the Moray Firth and the North Sea. He endeavoured to explain the origin of the shelly boulder clay by supposing that the Scotch ice which filled the basin of the Moray Firth was deflected by reason of the Scandinavian mer de glace, and was compelled to overflow the Caithness plain. In his volume on "Climate and Time," he quotes the testimony of one of the authors of this paper in proof of the gradual bending round of the Scotch land ice between

* Geo!. Mag., 1870, pp. 209-271.

"Climate and Time," p. 453.

page 7 the Orel and Dunbeath, on the east coast of this county. The evidence now referred to will be described when we come to discuss the direction of the ice-flow and the character of the boulder clay.

In 1871, a paper appeared in the Transactions of the Geological Society of Glasgow, by the Rev. Henry Crosskey and David Robertson, in which they give a short account of the boulder clay sections near Wick, along with a list of the Foraminifera obtained from that deposit.*

In the volume of the publications of the Palæontographical Society, published in 1874, Messrs G. S. Brady and Robertson, in their "Monograph on the Post-Tertiary Entomostraca," describe the boulder clay near Wick, and give a list of Entomostraca from the sections in Wick Bay and burn of Haster.

Before leaving this part of the subject, reference ought to be made to the labours of Mr Joseph Anderson, Curator of the Antiquarian Museum, Edinburgh. Though he is more widely known by his researches among "the Picts' Houses" in Caithness, yet, during his residence in Wick, be was an earnest worker at the present subject, and several observers have been indebted to him for valuable assistance. He was the first to wash the Caithness boulder clay for microscopic organisms—a process which has added greatly to the list of the fauna obtained from that deposit.

* "The Post-Tertiary Fossiliferous Beds of Scotland," by the Rev. ii. W. Crosskey and Mr D. Robertson, Trans, of the Geol. Soc. of Glasgow, vol. iii., p. 126, 127. This paper was read in 1868.

"Monograph of the Post-Tertiary Entomostraca," by Messrs G. S. Brady, the Rev. H. W. Crosskey, and Mr D. Robertson, Palaioutographical Soc., vol. xxviii., p. 7, 1874.