Humberside Geologist no. 10

Some Eighteenth Century Notes on Glacial Erratics in Humberside

by M.J. Boyd

In the Humberside County Record Office, at Beverley, there is preserved a series of ten letters written, between 1st July 1760 and 27th January 1761, by the well-known naturalist, antiquary and dealer in 'natural curiosities' Emanuel Mendes da Costa (1717-1791) to William Constable (1721-1791) of Burton Constable Hall in Holderness. Although these letters deal mainly with the numerous biological and geological specimens purchased from da Costa by Constable, they also include da Costa's answers to a number of questions, on scientific matters, put to him by Constable. Several of Constable's enquiries concerned what would nowadays be termed the Quaternary geology of North Humberside and da Costa's comments upon this subject are, in view of their date, of some historical interest. It is these comments, reproduced below, which form the basis of the present paper.

Emanuel Mendes da Costa was a Jewish merchant, of French and Portuguese extraction, who achieved a position of some eminence in the scientific circles of eighteenth century London. His main scientific interests lay in the fields of conchology and geology, and he amassed large collections of both shells and 'fossils' (the term 'fossil' was, in the eighteenth century, still used with a wider meaning than it has today and covered rocks and minerals, as well as fossils in the modern sense of the word). Da Costa was elected to Fellowship of the Royal Society in 1747 and became a Fellow of the Society of Antiquaries in 1752. Despite his scientific achievements and publications, da Costa is probably best-remembered today for the scandal attendant upon his embezzlement of some fifteen hundred pounds - a large sum in the eighteenth century - from the funds of the Royal Society. This scandal resulted in his imprisonment, the loss of his position as Clerk to the Royal Society and his formal expulsion from the Society of Antiquaries. As Whitehead (1977) has noted, "to earn a respected place in both the Society of Antiquaries and the Royal Society was not, in the eighteenth century, an uncommon achievement; but to be then expelled from the one and sent to prison by the other is altogether rare!"

William Constable, da Costa's customer and - to some extent - informal pupil, was an unusually learned and cultivated example of the scientific dilettante of the 'Age of Reason'. Debarred, by reason of his adherence to the Old Faith, from taking an active part in public life, he devoted himself to scientific study, the improvement of house and estate and the patronage of fine craftsmanship of all kinds. He undertook no less than three Grand Tours, and built up notable collections of scientific instruments, plant specimens and 'fossils'. His geological collection still survives, largely intact, at Burton Constable Hall (Boyd 1991) and is of considerable interest, for it is still housed in its original wooden cabinet and appears to be much as Constable himself left it.

Da Costa's first comments, in the correspondence under discussion, relating to the Quaternary geology of Humberside are contained in a letter dated 22nd July, 1760. Here, he advises Constable as follows :

"Now the coralloids which are found on your shores (all those at least I have seen) are worn round or smooth by the waves, and are like Pebbles; their proper name in English is Bowlder stones: they are brought by the Sea from other parts.

I would advise you always to carefully inspect the Bowlder stones on the shores; besides Coralloids, you often find Granites, some porphyries, some Jaspers, and other curious stones: which will amply repay your Science and sight, when polished, but I do not remember that your shore is any wise famed for them: however, perhaps the discovery is reserved for you, therefore be not dismay'd at once, but prosecute the researches with Assiduity: certain it is that the Lincolnshire shores of the Humber mouth (not far distant from you) afford a prodigious Harvest of such elegant Bowlder stones."

The precise nature of the "coralloids ..... worn round or smooth by the waves ..... like Pebbles" is not altogether clear, but the present writer would suggest that these may have been Lower Carboniferous corals (probably including Lithostrotion species) preserved in the glacial erratics of Carboniferous Limestone which are relatively common in the Skipsea Till of Holderness. With respect to these, as well as the other glacial erratics referred to in the passage quoted above, it is interesting to note that da Costa (quite correctly) regarded them as having been transported to Holderness from elsewhere - even though he made the (quite understandable) error of regarding the sea, rather than glacial ice, as the agency of transport.

Da Costa's next remarks concerning the geology of Humberside are to be found in a letter dated 14th August, 1760. He appears to be commenting upon a description, by Constable, of the boulder clay cliffs of Holderness :

"The sea cliffs are high and Earthy, say you: I cannot but think if you search after Tempestuous Weather, high tides &c, but you will meet with Shells, bones and teeth of fish &c; but depend they will not be in any good preservation: the Earthy particles are too lax to preserve them well."

With respect to the above passage, the present writer can only comment that, could da Costa have been aware of the actual conditions of deposition of the tills of Holderness, he might have been rather less optimistic about the chances of finding fish remains therein - and even more pessimistic about the likelihood of their "bones and teeth" being well-preserved!

In his letter of 1st November, 1760, da Costa gives his thoughts upon a number of geological specimens, from North Humberside, which had been sent to him by Constable. One of these specimens was a piece of amber from the coast of Holderness, and da Costa's comments with respect to this item are not without interest :

"No.l. Amber, very fine - in your letter you say that the stormy Eastern Winds will bring you plenty from Prussia, by which you seem to think that it is wafted to your shores from the Prussian coast. Pardon me to tell you that is a mistaken notion, for the Amber you sent and which is found on your shores, is absolutely a product of your coast, and is only dislodged from its Native bed, the Cliffs, by the stormy winds. Amber in like manner is found on several of our English coasts, as the Norfolk, Suffolk, & Essex shores &c, without being indebted to Prussia for its existence."

It seems clear from the above that Constable's opinion as to the origin of the Baltic amber which is found in small quantities on the shores of eastern England was that which is commonly held today. It is equally clear that da Costa disagreed with this view and regarded the amber as being derived from the eroding British coastline. Constable must have re-stated his opinion for, in his next letter (25th November, 1760), da Costa returns to the question of the origin of the Holderness amber and reiterates his view :

" - the Amber is certainly the product of some parts near Holderness, and is there wash'd up by the waves. For Amber is found on many of our English shores. As to its being only found after high winds, it must be so, As few things are ever found on strands but after storms: and after stormy weather is the best harvest for vertuosi to search the sea coasts."

Da Costa cannot, in the mid-eighteenth century, have had any conception of the real origin of the glacial tills of Humberside, Lincolnshire and East Anglia, but his (unconsciously implied!) suggestion that the fragments of amber found on the beaches of eastern England were originally incorporated in these tills as glacial erratics is, nonetheless, an interesting one.

The present writer would conclude by pointing out that some of da Costa's suggestions to William Constable on the subject of glacial erratics are as apposite today as they were two hundred years ago; and would urge the local geological vertuosi to continue to "search the sea coasts" and "always to carefully inspect the Bowlder stones on the shore."


Boyd, M.J. 1991. William Constable's 'Fossil Cabinet'. 42-47. In  Hall, I. and Hall, E. Burton Constable Hall. Hull City Museums & Button Press, Hull & Beverley, 104pp.

Whitehead, P.J.P. 1977. Emanuel Mendes da Costa (1717-91) and the Conchlogy, or natural history of shells. Bulletin of the British Museum (Natural History), Historical Series, 6 (1), 1-24.

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