Ordnance Datum Research Articles

Palæolithic Implements from the Hills near Dunstable

DURING the past twelve months I have found a small number of Palæolithic implements at great elevations in North Hertfordshire and South Bedfordshire, unconnected with existing river valleys. Four of the implements—1386, 1387, 1393, and 1398 in my collection—are from Caddington: height above Ordnance datum, 595 feet 9 inches. The dry valley close by, to the west, is 470 feet, and the ground gradually falls southwards to 409 feet at the source of the Ver, near Markyate Street, at a distance of 1 3/4 mile. The sections at Caddington exhibit red “clay with flints,” brick earth (or clay), and tenacious brown clay or loam, surmounted by blackish earth, containing broken white-coated flints, a few ochreous flints, and numerous blackish Tertiary pebbles. The whole deposit rests on chalk, and varies in depth from 2 feet to 50 feet. Aware of the importance of finding the worked flints in the undisturbed material, I have, after long searching, found a single implement and one or two flakes in situ at the stony bottom of the upper deposit of tenacious brown clay at a depth of 3 and 4 feet from the surface. A single small Palæolithic implement I have found on the surface at Kensworth: height above Ordnance datum, 759 feet 8 inches. The bottom of the valley, 1¼ mile to the west, at the source of the Ouzel, is 414 feet. Half an ovate Palæolithic implement, obviously derived from the hill-tops, I have found in a field at the bottom of a chalky valley near Houghton Regis. The Caddington implements are pointed (or tongue-shaped), slightly abraded, small in size, and cinnamon-brown in colour. The interest attached to these finds rests not only on the great heights mentioned and the positions away from existing river valleys, but in the nature, age, and mode of deposit of the upper tenacious brown clay in which the implements are embedded. The implements themselves agree in make and appearance with the well-known brown or ochreous implements often found in non-ochreous sand, &c., in existing river valleys. I have at present seen no traces of fossil bones or fresh-water shells in the deposits mentioned.

On the Cae Gwyn Cave, North Wales

Summary The recent researches at Cae Gwyn have proved most conclusively that there was no foundation for the views of those who contended that the drift which crossed over the entrance and extended into the cavern was remanié , and had gradually crept down the hill. They have shown beyond the possibility of doubt that the deposits which overlie the bone-earth are in situ , and are identical with the typical glacial deposits of the area. It was found also that these deposits had at one time extended continuously across the valley above this elevation (400 feet above ordnance datum), and that the caverns had consequently been completely buried beneath them. The explorations carried on in 1885, 1886, and 1887, in the Cae Gwyn and Ffynnon Beuno caverns, show that they must have been occupied by the animals before any of the Glacial deposits now found there had accumulated, also that a thick floor of stalagmite had formed over these remains before the caverns were subjected to water-action. This action broke up the floor and completely re-sorted the materials, evidently washing out some, but also adding sandy and gravelly material to the deposits. Very large blocks of limestone, which were found at many points in the caverns, had evidently been disturbed by the same force, and had in many cases protected the original contents; they were, however, invariably found in the lowest deposits, and were covered over by laminated clay, sands, and gravels. It is certain that the caverns had been completely filled

An Estimate of Post-Glacial Time

Of late several attempts have been made to show that the close of the Glacial period was very recent. Having personally devoted considerable attention to what is called Post-glacial or “superficial” geology, I am much struck with the imperfect knowledge with which the question of Post-glacial time is frequently approached. The writers seem to be unaware of, or to insufficiently appreciate, the grand sequence of events recorded in the deposits on the Lancashire and Cheshire coasts which have taken place since the snow and ice of the Glacial period disappeared. On the borders of the coast-line between the Dee, the Mersey, and the Ribble, the student who cares to pursue the subject can do so with great advantage. But through the horizontality of the deposits, and their general low level, none occurring above the level of the 25 feet Ordnance datum and all reaching down to below the level of the lowest spring-tides, the study has to be pursued through the medium of excavations and borings. This I have done in observations extending over many years, and I now propose to show their bearing upon the absorbing question of recent geological time. Denudation of the Low-Level Marine Boulder-clay. The whole of the country to which these notes specially refer was formerly entirely covered with a mantle of Low-level marine Boulder-clay and sands. These I have described at length in several papers. That the valleys of the Dee, Mersey, and Ribble were at one time filled with Low-level marine Boulder-clay, we

Account of a Well-sinking made by the Great Western Railway Company at Swindon; with Lists of Fossils

1. The Great Western Railway Company being desirous of obtaining good supply of water for use in their locomotive and stationary engines at Swindon, determined, in 1883, to sink a well. The spot chosen for this undertaking is on the northern side of the railway, and at the western end of the Company's works. Two shafts have been sunk, very close together―one known as the South Well, to a depth of 246 feet, and the other as the North Well, to a depth of 736 feet 2 inches. The details of the strata passed through in the two sinkings, to the depth of 246 feet, are practically the same, the shafts being 8 feet in diameter and sunk the entire depth. The object of the additional shaft was for convenience in pumping and in carrying away the material excavated. The surface of the ground is 329 feet above the Ordnance datum. From a practical point of view this well has not been altogether successful; for, although the promoters did not actually get into hot water, they tapped a supply of luke-warm and very saline water. The Corallian beds, which occur between the depths of 72 and 112 feet, yielded the first supply of water, which issued at the rate of about 1000 gallons per hour; but neither in quality nor in quantity was it deemed satisfactory. It contained 144 grains of saline matter per imperial gallon. Water again was met with at the depth of 730 to 736 feet, rising

On some Borings in Kent: a Contribution to the Deep-seated Geology of the London Basin

It will be of interest therefore to give a full account of these borings, of which only short notices have yet appeared, and to review the bearing that the result of the later one has on our knowledge of the underground formations of the London Basin. The borings are about 210 yards westward of the Factory Basin, in what was, until the extension of the docks was made, the marsh on the southern side of the former St. Mary's Creek, that creek having also been included in the new dockyard. The surface of the ground is about ten feet above Ordnance Datum. The earlier boring, which reached Lower Greensand at a depth of over 903 feet, being of small size, in the lower part at all events, it was resolved to put down another and larger one near by, in order to get a large amount of water from the Lower Greensand; and it is to the second boring that this paper chiefly refers, because of the unforseen result. One would have thought that Chatham was favourably placed for getting a large suply of water from the Lower Greensand, which formation has a broad outcrop only a few miles to the south. It was therefore with some surprise that one heard that, after passing through only 41 feet of sandy beds (below the Gault), a mass of clay was reached at the depth of 943 feet. At first this clay was naturally taken to be either a very clayey development

Societies and Academies

Societies and Academies

On the Nature and Relations of the Jurassic Deposits which underlie London

The well and bore-hole (see fig. 1, p. 744) which have revealed the particulars of the strata described in this paper are sunk on the premises of the Richmond Vestry Waterworks, situated about 160 yards below Richmond Bridge, on the right bank of the Thames. The common centre of the well and bore-hole is about 33 yards distant from the high-water line of ordinary spring tides. The altitude of the surface of the bore-hole is about 17 ft. above Ordnance datum. The well, which has an internal diameter of 7 ft. at top and 5 ft. at the bottom, was sunk in 1876 for the purpose of supplying water to the town of Richmond, and was carried down to the Chalk, which was met with at 253 ft. below the surface. From the bottom of the well a 24-in. bore-hole was further sunk to the total depth of 434 ft., thus penetrating 181 ft. into the Chalk. This well and bore-hole were completed in the summer of 1877. The Tertiaries passed through were represented by 160 ft. of London Clay, 60 ft. of the Woolwich and Reading beds, and some underlying sands. Down to 434 ft. the writer of this notice was in no way connected with the carrying out of the work; Messrs. Russ and Minus being the engineers under whose direction the well and bore-hole to the depth before stated were executed. Samples of the Tertiaries passed through were kept, and can be inspected at the office of

The Storm of January 26

DURING this storm there was a remarkable depression of the barometer, it falling to 26.9, as shown in the accompanying chart. The lowest depression last year was 28.2 on Nov. 25. Lurgybrack lies in lat. 54° 56′ N., and long, 7° 42′ W. It is 225 feet above the Ordnance datum level. A nearly similar depression was observed at Letterkenny, 140 feet above the Ordnance datum level. The wind veered round from the north-west by north and east to the south, and from the latter by west to north. The storm was succeeded by a fall of snow, which has now melted away.

Tides at Chepstow

I OBSERVE two letters in NATURE lately upon this subject. Many years ago I took some pains to ascertain the greatest known rise of tide at Chepstow, for I doubted the accuracy of the common statement that it was seventy feet and upwards. At the time I made the inquiry the large railway bridge at Chepstow to carry the South Wales Railway across the River Wye was being constructed. I was acquainted with Mr. Oakden, one of the engineers on the work, and he, with great care, took levels of the marks which had been made from time to time recording the very high tides, some of them going back many years. He found the highest of them to be some decimal (of which I have no record) above fifty feet above ordnance datum. I think this may be relied upon. It is corroborated in a paper by the present Astronomer-Royal, on “Tides and Waves”, in the “Encyclopaedia Metropolitana”, vol. v. p. 242, paragraph 7, first edition. He says: “Thus, at the entrance of the Bristol Channel the whole rise at spring-tides is about eighteen feet, at Swansea about thirty feet, and at Chepstow about fifty feet”.

On Quaternary Gravels

I n continuation of a paper on this subject in the Quart. Journ. Geol. Soc. vol. xxiv. p. 103, I now submit a number of measured sections selected as instances of the deposition of gravels of different character under different circumstances both of height above the sea-level and distance from the sea. The illustrations and remarks in this paper relate to the unfossiliferous gravels of the rivers Taff, Rhondda, and Cynon, in Glamorganshire, South Wales, to those of the Aire, in Yorkshire, and to the fossiliferous gravels and brick-earths of the lower part of the Thames and Lea rivers, in the counties of Kent and Essex. One section of the fossiliferous gravel of the river Avon, at Salisbury, is given for the purpose of comparison with those of the Thames; and a section across the valley of the Aire, in Yorkshire, is compared with those in the valleys of the Taff and Rhondda. A map of part of Glamorganshire, and a longitudinal section of the bed of the river Taff, with the heights along its course measured above the height of spring tides at Cardiff, have been prepared to define the exact locality of the Welsh gravels alluded to. A similar map and sections of the course of the river Aire, in Yorkshire, with heights measured from the Ordnance datum, are given for comparison with the Welsh illustrations. A sketch-map of part of the river Thames, and of the adjoining counties of Kent and Essex, and separate maps, on a large