Part 3

As the greater portion of the subjacent rocks of the county is formed by the Chalk, it will be convenient to commence with this formation. The Chalk extends, or “strikes,” across all but the south-eastern portion of the county in a broad belt, with a general south-westerly or north-easterly direction, reaching on the northern side, with a few exceptions, to the border of the county and beyond, while to the southward its boundary runs approximately through Bushey, South Mims, Hertford, and Bishop’s Stortford. At Dunstable the Chalk forms what is called an “escarpment,” that is to say a high and somewhat precipitous (although rounded) cliff overlooking the great plain formed by the marls and clays of the underlying strata. As in all true escarpments, the beds, or strata of the Chalk, which are somewhat tilted by earth-movements out of their originally horizontal plane, incline, or “dip” away from the main face of the cliff, that is to say, towards the south-east; and this south-easterly dip of the Chalk, apart from local interruptions and folds, continues to its southerly boundary. Now since the Chalk is a porous formation admirably fitted to collect and retain the rain-water falling upon it, while it is underlain, as we shall see shortly, by the impervious Gault Clay of the Bedfordshire plain, and overlain along its southern boundary by the equally impervious London Clay, it is obvious that it will hold all the water thus collected, and that this water will tend to run deep down in the rock in a south-easterly direction. Hence the northern part of the Chalk zone forms an almost perfect water-collecting area, which can be tapped along the southern side of the county by boring through the overlying London Clay.

The Chalk comprises several main divisions, of which the highest is known as the Upper Chalk, or the Chalk with flints; this when fully developed being about 300 feet thick. It is a soft white limestone traversed by nearly horizontal layers of black, white-coated flint, which have originated by a process of “segregation” in the rock subsequent to its deposition as ooze on the old sea-bed. Usually these layers consist of irregular nodular masses; but there is sometimes a continuous thin layer of scarcely more than half-an-inch in thickness, locally known as “chimney-flint.” The south-easterly dip of the Chalk is shown by the layers of flint to be not more, as a rule, than three or four degrees. The Upper Chalk extends from the summits of the hills as far down as Rickmansworth, Watford, Hatfield, and Hertford, thus forming the bed-rock of the greater portion of the county. By the wearing away of the overlying Tertiary strata, a small cone, or “inlier,” of Chalk is exposed at Northaw.

Next comes a bed of about four feet thick known as the Chalk-rock. It is a hard cream-coloured rock, containing layers of green-coated nodules, is traversed by numerous vertical joints, and rings to the stroke of the hammer. Owing to its hardness, it resists the action of the weather, and is therefore in evidence at or near the summits of the hills, where it can be traced from close to Berkhampstead Castle by Boxmoor and Apsley, and thence to the south-west of Dunstable, Kensworth, the south of Baldock, and so in a north-easterly direction to Lannock Farm.

Below the Chalk-rock we come to the Middle Chalk, or Chalk without flints, which may be so much as 350 feet in thickness, and rises in a rather steep slope or “step” from the underlying beds to be next mentioned. Flints are few and far between in the Middle Chalk, which forms the western slope of the Downs at Royston, as well as beyond the limits of the county at Luton, and so on to the Chiltern Hills. Fossils are much more numerous in the Middle than in the Upper Chalk. The lowest bed of the former is the Melbourn Rock, a hard, nodular band about 10 feet thick. Next comes the grey and white Lower Chalk, from 65 to 90 feet thick, after which we reach the Totternhoe Stone. Although only six feet in thickness, this Totternhoe Stone, which forms the escarpment of Royston Downs, is of importance as having been largely employed in the construction of churches and other buildings on the northern side of the county. It is a sandy grey limestone, which used to be largely quarried at Totternhoe, with special precautions in drying. It can be traced from Tring by way of Miswell, Marsworth, Pirton, and Radwell to Ashwell.

The Totternhoe Stone really forms the top of the Chalk-marl, which is some 80 feet thick, and consists of buff crumbling marly limestones. It forms a strip of low ground at the base of the Chalk escarpment. At the bottom of the Chalk occurs the so-called coprolite-bed, which contains large quantities of phosphate nodules. Forty years ago these beds were extensively worked between Hitchin and Cambridge for the sake of the nodules.

Only on the northern border of the county, between Hitchin and Baldock, and also near Tring and then merely to a very small extent, are any of the beds underlying the Chalk exposed. These comprise, firstly the Upper Greensand, which is either a sandy marl or a sandstone with green grains, and secondly, a dark blue impervious clay known as the Gault. These formations constitute the plain at the foot of the Chalk hills in Bedfordshire, the scenery of which is very similar to that of the London Clay plain in eastern Hertfordshire and Middlesex.

It is important to add that, at a gradually increasing depth as we proceed south, the Gault underlies the whole of the Hertfordshire Chalk, and renders the latter such an excellent water-bearing formation. If the Gault be perforated we come upon the Lower Greensand, another excellent water-bearing stratum, which comes to the surface in the neighbourhood of Silsoe, in Bedfordshire.

We may now turn to the formations overlying the Chalk in the southern half of the county. Here it should be mentioned that all the formations hitherto described overlie (or underlie) one another in what is termed conformable sequence; that is to say, there is no break between them, but a more or less nearly complete passage from one to another. Between the Chalk and the overlying Tertiary formations, there is, on the other hand, a great break or “unconformity”; the surface of the Chalk having been worn into a very irregular contour, above which we pass suddenly to the Tertiary beds, generally containing at their base a number of rolled chalk flints. This indicates that before the Tertiary beds were laid down, the Chalk had become dry land; after which a portion of it once more subsided beneath the ocean. The Tertiary beds are in fact formed for the most part from the _débris_, or wearing away of the old Chalk land.

The lowest Tertiary stratum of eastern and southern Hertfordshire is known as the Woolwich and Reading beds. These consist of alternations of bright-coloured plastic clays and sandy or pebble-beds; their maximum thickness in the county being about 35 feet. They form a band extending from Harefield Park to Watford, and thence to Hatfield and Hertford. Below the Woolwich and Reading beds we come on the London Clay, of which the basement bed contains a layer of flint pebbles, although the remainder of this thick formation is a stiff blue clay, turning brown when exposed to the action of the weather. Originally these Tertiary formations must have extended all over the Chalk of central Hertfordshire, as is demonstrated by the occurrence of patches, or “outliers,” of them over a zone of considerable width. Such Tertiary outliers occur at Micklefield Hall, Micklefield Green, Sarratt, Abbot’s Langley, Bedmond, Bennet’s End, and Leverstock Green, and in the northern, or St Peter’s portion of St Albans.

Closely connected with these Tertiary formations is the well-known Hertfordshire pudding-stone; a conglomerate formed of stained flint-pebbles cemented together by a flinty matrix as hard as the pebbles themselves, so that a fracture forms a clean surface traversing both pebbles and cement. This pudding-stone is usually found in the gravels (or washed out of them) in irregular masses, weighing from a few pounds to as many tons. It is stated, however, to occur in its original bedding between Aldenham and Shenley; and the rock evidently represents a hardened zone of the Woolwich and Reading beds. Pudding-stone is found in special abundance at St Albans and again in the neighbourhood of Great Gaddesden. In some St Albans specimens the pebbles are stained black for a considerable thickness by the oxides of iron, while the central core is bright red or orange. Such specimens, when cut and polished, form ornamental stones of great beauty; but, on account of their hardness, the expense of cutting is very heavy.

Except on the higher part of the Chalk Downs, and very generally along a narrow band half way up the sides of the valleys, the aforesaid formations are but rarely exposed in the county at the surface, on account of being overlaid with superficial deposits of gravel, clay, etc., which are of post-Tertiary age, and were deposited for the most part during the time that man has been an inhabitant of the world. These superficial beds are very frequently termed “drift,” on account of a large portion being formed by ice, at the time that northern Europe was under the influence of the great glacial period. Over most of the chalk area the denuded surface of the Chalk is covered with a thick layer of stiff clay full of flints, this layer being formed by the disintegration of the Chalk itself, the soluble calcareous portion being dissolved and carried away, while the insoluble flints and clay remain. Above this layer in the neighbourhood of Hertford, Barnet, and elsewhere, is a series of gravelly beds assigned to the middle division of the glacial period; while these in turn are overlaid locally, as at Bricket Wood, between St Albans and Watford, by the chalky Boulder-clay, of upper glacial age, which is there some twenty feet in thickness. In other places, as at Harpenden, the hills are capped by a still greater thickness of clayey deposits, mingled with flints, resting upon a very irregular surface of Chalk, which appears to be for the most part of glacial origin. Speaking generally, Boulder-clay is characteristic of the east, and clay with flints and gravel of the western side of the county.

Half way down the sides of the hills, in the district last named, the Chalk is more or less completely exposed at the surface along a narrow zone, below which we come upon deposits of gravel, sand, and clay filling the bottoms of the valleys. At Bowling Alley, Harpenden, these deposits are fully forty feet in thickness. Although they have been supposed to be the result of river action, it is more probable that they are due to rain-wash. Indeed this is practically proved in the case of the valley leading from Harpenden towards No-Man’s-Land, where the lower end is blocked by a ridge of gravel, which could not possibly have been formed by river action. The stones in these valley-gravels are of irregular shape, and thus quite different from the rounded pebbles of the gravels of the Woolwich and Reading beds, as seen at St Peter’s, St Albans. At Harpenden the uppermost layer of valley-gravel is extremely clean and sharp, generally of a golden yellow colour with blackish veins. Deposits of brick-earth occur locally throughout the Chalk area.

Over the greater part of the county the soil is the result of the decomposition of the foregoing superficial formations; and is consequently in most cases of a stiffer and more clayey character on the hill-tops than in the valleys, where it frequently forms only a bed of a foot, or even less, in thickness above the sharp, running gravel. Everywhere in the Chalk districts the soil contains a vast number of flints; but it is, nevertheless, admirably adapted for corn-growing, and especially for malting-grain; Hertford being one of the four English counties best suited to crops of the latter nature. On many of the unenclosed commons the soil is, however, of a poor and hungry nature, producing various kinds of inferior grass, together with spring-flowering gorse, as on Harpenden Common, or heather, as at Kingsbourn Green, between Harpenden and Luton, and at Gustard Wood, near Wheathampstead. On the higher Chalk Downs near Dunstable and Royston there is little or no soil properly so-called; the short, but sweet and nourishing grass growing on the chalk itself. A very different type of soil obtains in the London Clay area in the south and east of the county; this being heavy and clayey, and thus better suited for grass than for corn; in fact in the old days the Middlesex portion of this district was known to the country people as the “Hay-country.” Along many of the river-valleys peaty soils of a marshy and swampy nature prevail.

7. Natural History.

In former days, when the mammoth or hairy elephant, the extinct woolly rhinoceros, and the wild ox, together with the African hippopotamus and spotted hyaena roamed over the Thames valley and afforded sport to our prehistoric ancestors, England was joined to the Continent across what is now the English Channel; so that the animals and plants of the southern portion of our islands, at any rate, were more or less nearly identical with those of France and Belgium. The advent of the great ice age, or glacial period, caused, however, a vast disturbance of the fauna and flora (as the assemblages of animals and plants characteristic of different countries are respectively termed), especially as about this time there occurred several oscillations in the level of our country, during one or more of which Great Britain was temporarily separated from the Continent. How much or how little these and other changes had to do with the poverty of the British fauna as compared with that of the Continent is too long and difficult a question to be discussed in this place; but certain it is that even the southern counties of England do possess fewer species of animals and plants than France or Belgium; that this poverty increases with the distance from the Continent; and that Ireland is much poorer in species than England. It may perhaps be well to add, although it does not really concern our subject, that there appears to have been another land-connection by means of which Scotland and Ireland received a portion of their faunas from Scandinavia by way of what is now the North Sea.

At the date of the final insulation of Great Britain from the Continent there is every reason to believe that all the land animals of the former were identical with species inhabiting adjacent regions of the latter. And even at the present day, when isolation has for centuries been exerting its influence on the non-migratory (and in some degree also on the migratory) animals, there are no species of quadrupeds (mammals), birds, or reptiles absolutely peculiar to our islands, with the exception of the grouse; and in the opinion of many naturalists that bird should be regarded rather as a local variety or race of the willow-grouse of Scandinavia than as a distinct species.

Minor variations, however, characterise many, if not indeed all, of our British quadrupeds and birds when contrasted with their continental representatives. The British squirrel is, for instance, very markedly distinct from all the continental races of that animal in the matter of colouring, while somewhat less decided differences characterise our badger, hare, field-mice, etc. Similarly, among birds, the British coal-tit is so decidedly distinct from its continental representatives that it is regarded by some naturalists as entitled to rank as a species by itself; and minor differences from their continental cousins are displayed by the British redbreast, bullfinch, great titmouse, and many other resident species. Indeed, if careful comparisons were instituted between sufficiently large series of specimens, it is almost certain that all species of resident British land animals, as well as exclusively fresh-water fishes, would display certain differences from their foreign representatives; while in some instances, at any rate, as is already known to be the case in regard to certain species, more than one local race of an animal may exist in our own islands.

It is, however, a question as to what is to be gained by the recognition of such comparatively trifling local differences in animals (and still more by assigning to them distinct technical names), as the splitting process may be carried to an almost endless degree. A large London fishmonger is, for instance (as the writer is informed), able to distinguish a Tay from a Severn or Avon salmon; while a wholesale game-dealer will in like manner discriminate between a Perthshire and a Yorkshire grouse. In like manner a Hertfordshire badger or stoat may be distinguished from their Midland or North of England representatives; but it is difficult to see in what respect we should be the better for the recognising of the existence of such differences.

Accordingly, the fauna and flora of Hertfordshire may be regarded for all practical purposes as more or less completely identical with that of the south-east of England generally; and nothing would be gained, even if space permitted, by giving lists of the species which have been found within the limits of our county.

The fauna and flora of Hertfordshire, like those of other counties with varying geological formations, are not, however, by any means the same everywhere. On the contrary, there are well-marked local differences mainly associated with what naturalists call “station”; that is to say, differences of elevation, soil, geological formation, climate, etc., etc. The animals and plants of the high chalk downs in the neighbourhood of Gaddesden, Dunstable, and Ashwell, are for instance more or less markedly distinct from those of the lower level corn-growing areas of the centre of the county. On these elevated tracts we find, for example, wheatears, stone-curlews (near Tring), blue butterflies, burnet-moths, small brown-banded white snails, a periwinkle-like snail with a horny door to its shell known as Cyclostoma, blue gentians, certain orchids, and many other kinds of plants rarely or never seen on the low grounds. The open commons and heaths, on the other hand, as has been already mentioned, are the home of heather and gorse, together with various distinctive birds and reptiles, such as stonechats, whinchats, titlarks, goldfinches, vipers, slow-worms, and lizards. In the river-bottoms and other swampy localities we find marsh and water-birds, such as yellow wagtails, snipes, sandpipers, grebes (at Tring), herons, moorhens, water-rails, coots, dabchicks, and wild duck, together with (locally) the common grass or water snake, amber-snails, marsh-marigolds, purple loose-strife, ragged robin, reeds, and yellow flags.

Beech trees, as mentioned above, form the predominant timber on the chalk-lands other than the high downs, while on the heavier soils of the centre of the county their place is mainly taken by elm and ash. On these lowlands and other open cultivated tracts are found such birds as partridges, corncrakes, lapwings, pipits, and larks; while in the coppices, hedgerows, and gardens we look for nightingales (from which bird Harpenden takes its name, _haerpen_ being a nightingale and _dene_ a valley in Anglo-Saxon), blackcaps, whitethroats, wrens, and nuthatches; while the woods are the resort of green and spotted woodpeckers, wood-pigeons, jays, and pheasants. The low grass-growing clay-plains on the southern side of the county support, as already stated, an abundant growth of oaks to the almost complete exclusion of other timber trees; and this area doubtless also presents certain peculiarities in its fauna distinguishing it from the corn-growing tract to the north. The oaks grow to a very great size, especially at Sacombe and Woodhall Park, and three notable specimens in the county are Queen Elizabeth’s oak at Hatfield, Goff’s oak at Cheshunt, and the Panshanger oak.

In addition to these local peculiarities in the fauna dependent upon elevation, geological formation, soil, and the presence or absence of forest, there are, however, certain others for which climate may possibly account.

A case in point is afforded by the distribution of stag-beetles and magpies in the county. Both these species are unknown in the district immediately round Harpenden, while the former, at any rate, are likewise unknown in the St Albans district, and apparently between that city and London. If, however, we travel from Harpenden to the east, magpies may be met with when we reach Codicote, while in the opposite direction they occur in the Hemel Hempstead district. As to the exact point where stag-beetles make their appearance in the latter direction the writer has no information, but they are to be met with in the neighbourhood of Rickmansworth and elsewhere on the Buckinghamshire border, and become quite common in that county. Grass-snakes, so far as the writer is aware, are likewise absent from the Harpenden neighbourhood, although on the Cambridgeshire side of the county they are quite common, as they are across the border.

If the local distribution of these species were carefully worked out and mapped, we might perhaps be able to account for what is at present a puzzle.

With the increase of population and building the wild fauna of Hertfordshire, like that of England generally, has been gradually becoming poorer in species--probably indeed from the time the mammoth and the woolly rhinoceros were exterminated, as they possibly were, by our prehistoric ancestors. When the wolf, the bear, the wild cat, and the beaver disappeared, is quite unknown; but it is in comparatively modern times that the marten has been exterminated, a solitary individual of this species having been killed in the county within a score of miles of London, that is to say near Watford, so recently as December, 1872. Polecats appear to have almost if not quite disappeared from the county, although a straggler may occasionally enter from Buckinghamshire, where a few still survive; and one was trapped in Ware Park about 1885. Otters are rare, although a few occasionally appear in the lower part of the Lea valley, and some may enter the county from Buckinghamshire, in parts of which they are much more common, the Buckinghamshire Otter-hounds having killed over a score of these animals in 1908. Some years ago badgers were to be found in many parts of the county, a well-known haunt previous to 1840 being “Badger’s Dell” in Cassiobury Park. They still occur locally in certain parts of the Buckinghamshire side of the county, and probably elsewhere. Foxes owe their preservation mainly to the sporting instincts of the county gentry and farmers.

Among birds that have disappeared from the county, the most to be regretted is the bustard, which in the early part of last century was still to be found in the neighbourhood of Royston, although the precise date of its extermination from this part of England is unknown. The bittern, too, is, at the very most, known only as an occasional straggler; but a specimen was shot in a small marshy pond on Harpenden Common some time previous to 1860. The Royston crow, by some naturalists held to be only a form of the common crow, has been named from the Hertfordshire town, though a widespread species throughout many parts of Europe.