A beach is built up of water-worn pebbles, consisting usually of bits of the rock of the immediate vicinity, which have become rounded and shaped by continually rolling and knocking against one another as the waves of the sea throw them up or drag them down the sloping heap of like pebbles which is accumulated near high-water line. At Dover and such places, under chalk cliffs, the beach consists of chalk pebbles oval in shape, often of 8 or 9 inches in length, with a large number of well-rounded flint pebbles as big as your fist interspersed, or outnumbering the chalk pebbles. At Tenby, in South Wales, the beach consists of assorted sizes of limestone pebbles, well-worn bits of the limestone cliffs of the neighbourhood. Large numbers of them are literally "worm-eaten," being bored into, hard and dense as they are, by a little marine worm (known as Polydora), which may be sometimes found alive and at work in these limestone pebbles lying between tide limits, or more easily at other places in similarly placed chalk blocks or pebbles. On a coast bounded by granite cliffs you get a beach of granite pebbles; where there are cliffs of slate or of sandstone, pebbles of slate or of sandstone.
But there are some beaches which, as remarked above, are continually travelling along the coast. That on the English shores of the North Sea, for instance, is always moving southwards, except where it is held by piles and breakwaters, locally called "shies." Moreover, the land of the East Coast, especially the Suffolk and Norfolk coast, in the course of its erosion, has given back to the sea old deposits of the glacial and post-glacial period, consisting of gravels and "drift," made up of flint pebbles and fragments of rocks from the more northern regions over which the great European ice-cap of the glacial epoch extended, and from which it ground and tore the surface rock and carried large and small masses—boulders and incredible millions of tons of broken up fragments—and spread them over East Anglia (where they form the so-called "glacial drift"), and over regions still submerged in the North Sea. Consequently the beach on the Suffolk seashore has a specially variegated assortment of pebbles from all sorts of more northerly situated rocks—though small flint pebbles, derived directly from glacial drift and by the drift from the chalk land-surface (the chalk itself not now reaching the shore-line of East Anglia), are greatly predominant. It is in the chalk that flint takes its origin, being found there as large irregular nodules and sheets.
CHAPTER VII
THE CONSTITUENTS OF A SEABEACH
I ONCE went down to Aldeburgh, on the Suffolk coast, with a party of friends, which included an American writer, himself as delightful and charming as his stories. Why should I not give his name? It was Cable, the author of "Old Creole Days." We walked through the little town to the sea-front, and came upon the immense beach spreading out for miles towards Orford Ness. "Well, I never!" said he to me; "I suppose the hotel people have put those stones there to make a promenade for the visitors. It's a big thing." It took me some time to persuade him that they were brought there by the sea and spread out by it alone. It was his first visit to Europe, but he had seen the seashore on the other side, and there was nothing like this over there, he declared. A similar readiness to ascribe Nature's handiwork to the enterprise of hotel-keepers led a visitor to the Bel Alp, in the Rhone Valley, when he looked down from that high-placed hostelry on to the great Aletsch glacier, with its central "moraine" of huge rock masses and debris, to exclaim, "I see the proprietor has spread a cinder-path along the glacier to prevent us from slipping. It's a convenience, no doubt, but gives a nasty dirty look to the snow." Mr. Cable, when he once realized that the great Aldeburgh beach was a natural production, did what a true poet and naturalist must do—he fell in love with it, and spent hours in filling his pockets with strange-looking pebbles of all kinds until he was brought into the house to dinner by main force, when he spread his collection on the table, and demanded an explanation of "what, whence, and why" in regard to each pebble. Our companions—a great lawyer, a military hero, a politician, and two "learned men"—regarded him as eccentric, not to say childish. But I entirely sympathized with him, and when next day we sailed down to Orford and stood in front of the old Norman fortress, he further established himself in my regard by deeply sighing and exclaiming, "So that is a real English castle!" whilst several large tears quietly streamed down his undisturbed countenance.
To give an idea of what various rocks from far-distant localities may be brought together on an East Coast beach, take that of Felixstowe as an example. What is true of the East Coast is to some extent also true of the South Coast, and, indeed, wherever the sea makes the pebbles of a modern beach from the materials furnished by the breaking up of old deposits, which were in their day brought by ice-flows or torrential currents from remote regions. The most abundant kind of pebbles on the Felixstowe beach are small, rounded, somewhat flat pieces of flint, derived not directly from the chalk which is the "stratum" or "bed" in which flint is originally formed, but from the Red Crag capping the clay cliffs (London clay or early Eocene), and also from surface washings and "gravels" (of later age than the crag) farther north, whence they have travelled southward with many other constituents of the beach. All these flints are stained ruddy brown or yellow by iron—a process they underwent when lying in the gravels or in the crag in which they were deposited as pebbles, broken, washed, and rolled ages ago from the chalk. The iron is in a high state of oxidation, and stains not only flint pebbles but the sands of the Red Crag and later gravels a bright orange-red, or sometimes a less ruddy yellow. The iron comes originally from very ancient igneous rocks in which it is black and usually combined with silica. The chalk flints are always, owing, it seems, to minute quantities of carbon, quite black in the mass, but thin, translucent splinters have a yellowish-brown tint. The flints are free from iron stain when taken direct from the chalk. The commonest pebble next to flint is milky quartz, or opaque white quartz. This is derived from some far northern source, where there are igneous rocks traversed by veins of this substance (perhaps Norway). Quartz, like flint, is pure silica, the oxide of the element silicon. It appears in another form as rock-crystal, and also as chalcedony and agate. Opal also is pure silica, but differs from quartz and its varieties in being non-crystalline or amorphous, and in being less hard and of less specific gravity than quartz. Opal is soluble in alkaline water containing free carbonic acid, such as are many natural waters and the sea! But quartz is not so. The siliceous "spicules" and skeletons of many microscopic animals and plants are "opal." The gem known as "opal" is a variety owing its beauty to minute fissures in its substance which break up light into the prismatic colours.
A great deal rarer than the milky quartz, but well known on the East Coast on account of their beauty, and often sought for to be cut and polished, are the small rolled bits or pebbles of chalcedony or agate, which have been bedded before their appearance on the beach in some of the pre-glacial or post-glacial gravels, together with the flints, and in consequence are often stained of a fine red. Such clear red-stained chalcedony is called "carnelian"; if the banded agate structure shows, it is called agate rather than carnelian. It is wonderful how many beautiful pieces of both carnelian and agate are picked up on the Felixstowe beach, rarely, however, bigger than a hazel nut. The original source of these carnelians and agates is the East of Scotland. At Montrose you may see the igneous rock containing pale, lavender-coloured agate nodules as big as a potato, the breaking and rolling of which by the sea into small bits has furnished our Suffolk carnelians. Quartzite—more or less translucent, sandy-looking pebbles, colourless or yellow: jasper, black or green with red veining: a fine wine-red or purple stone often veined with quartz—are all more or less common, and come from northern igneous rocks—possibly some from Scandinavia and some from the breaking up of an ancient "breccia" of the Triassic age, which still exists northwards of East Anglia.
Other pebbles very common on this shore are those formed in a curious way by the sea-water from the clay cliffs and sea bottom which are here present, and are of that special geologic age and character known as the London clay. The sea at this moment is continually converting the clay of our Suffolk shore into "cement-stone" by a definite chemical process. The clay and many other things submerged in the sea, as Shakespeare knew, "undergo a sea-change." The cement-stone used to be dredged up from the sea bottom and ground to make cement at Harwich. Great rock-like slabs of it pave the shore at low water, and pebbles of it are abundant. The curious thing is that ages ago—geological ages, I mean—when the sea was throwing up here the old shell-banks and sand-banks known nowadays as "the Red and Coralline Crags," the London clay cliffs and clay sea bottom were in existence just as they are now. But in that period there existed here enormous quantities of bones of whales of kinds now extinct, which had lived a little earlier in the sea of this area, and were deposited in vast quantity as a sort of first layer of beach or shallow water sea-drift. Bones consist largely of phosphate of lime, and are used as manure. In that old crag sea the phosphate of lime was dissolved from the deposit of bones, and as we find occurring in the case of other clays and other bones elsewhere—was chemically taken up by the clay—the same kind of clay which to-day is being converted into "cement-stone." It was thus, at that remote period, converted into "clay phosphorite," owing to the presence of the immense deposit of whales' bones, and it has been known for sixty years as Suffolk "coprolite," owing to a mistaken notion that it was the petrified dung of extinct animals. It has been dug up by the ton from below the crag all over this part of Suffolk, where it forms, together with bones, teeth, flints, and box-stones, a bed of small nodules, a foot or so thick separating the London clay from the shelly "crag." This bed is called the Suffolk bone-bed or nodule-bed. The phosphorite, or "coprolite," occurs in the form of bits of clay, hardened by phosphate of lime, and of the colour of chocolate, and hundreds of tons of it have been used by manufacturers of the manure known as "superphosphate." Henslow, of Cambridge, Darwin's friend and teacher, was the first to point out its value. Bits of it, as well as box-stones, and fragments of bone, teeth of whales, of sharks, of mastodon, rhinoceros, tapir, and other extinct animals—all fallen from the bone-bed in the cliff—are found mixed with the pebbles of the Suffolk beach by those who lie on that beach in the sunshine, and, for want of something better to do, turn over handful after handful of its varied material. And, besides all the stones I have already mentioned, they find amber, washed here by some mysterious currents from the Baltic, wonderful fossil shells out of the crag, the cameo shell, and the great volute,—shells which are as friable as the best pastry when dug out of the Red Crag, but here on the shore become hardened by definite chemical action of the sea-water, so as to be as firm as steel. Here, too, the "chiffonier" of the seashore finds recent shells, recent bones (slowly dissolving and wearing away), well-rounded bits of glass, jet drifted down from Whitby, Roman coins, bits of Samian ware (!), mediaeval keys, bits of coal, burnt flints (from steamers' furnaces), and box-stones.