Fourth Report of the Committee, consisting of Professor HARKNESS, Prof. PRESTWICH, Prof. HUGHES, Rev. H. W. CROSSKEY, Prof. W. BOYD DAWKINS, Dr. DEANE, Messrs. C. J. WOODWARD, L. C. MIALL, G. H. MORTON, and J. E. LEE, appointed for the purpose of recording the position, height above the sea, lithological characters, size, and origin of the more important of the Erratic Blocks of England and Wales, reporting other matters of interest connected with the same, and taking measures for their preservation. Drawn up by the Rev. H. W. CROSSKEY, Secretary.

THE Committee has pursued the same course as during former years. The time for generalization has not yet arrived. There are many erratic blocks scattered over the country as yet unrecorded, and their character and distribution will largely affect any conclusions that may ultimately be reached. The Committee has for its present duty the collection of facts; when its labours have resulted in a complete account of the isolated boulders and groups of boulders of England, Wales, and Ireland, material now unavailable will exist for theoretical discussion, and many important incidents in the history of the glacial epoch will be more accurately determinable.

The importance of the work undertaken by the Committee continues to be emphasized by the destruction which is constantly going on. War is waged upon the boulders (which in many cases are our only source of information respecting the epoch to which they belong) by agriculturists, and builders, and road-makers with unceasing energy. They are built into walls, buried in the earth, used as foundation-stones, and often blasted to pieces; their preservation is difficult to secure, on account of their interference with the culture of the land. In a few years it is not too much to say that the evidence of glacial phenomena will in many districts be almost effaced.

The Committee directs attention to (1) the distribution of erratic boulders from different centres of ice action; (2) the agencies by which they have been transported; (3) the different periods in the glacial epoch to which they belong; (4) the heights above the sea at which they are found, indicating large changes in physical geology.

The schedule of inquiry, indicating the various points of the information. required, printed in a former Report, has been issued, and copies may always be had on application to the Secretary of the Committee.

DEVONSHIRE.

A very remarkable group of boulders has been reported upon by Mr. George Doe, of Great Torrington.

It is found in the estate of Rivalton, in the parish of Langtree, Devon, about four miles from Great Torrington.

The dimensions of the largest boulder of the group are 13 ft. x 6 ft. x 3 ft. It is subangular in form; but there are no groovings or striations. It rests on clay, close to a small brook, and is about 500 feet above the sea-level. The only legend connected with it is the old story of its having been thrown by the Devil.

At the distance of about 25 ft. N.E. is another boulder 3 ft. × 34 ft. x 24 ft. At a distance of 35 yards are six small boulders, cropping out from the ground.

At a distance of nearly half a mile are three more, similar to the last mentioned.

Near them is a deposit of flints in clay and a gravel-pit.

All these blocks except the first are south of the large boulder. These boulders consist of felsite, resembling that in many of the "Elvans." A felsitic Elvan, at Tresavaen, Gwen-nap, Cornwall, cannot be discriminated from them. Possibly, however, a nearer locality may be found.

OXFORDSHIRE.

Professor Prestwich describes a boulder found last summer, near Oxford, in a bed of subangular flint-gravel (high-level river-gravel), at Wolvercote brick-pit, on the high road from Oxford to Woodstock, at an altitude of about 40 feet above the level of the river Isis.

It consisted of a mass of hard saccharoid sandstone of concretionary origin, some portion of it broken away, and the broken edges quite angular; it weighed about three tons. It bore no trace of ice-scratches. There were no fossils to identify the sandstone; but from general characteristics, Professor Prestwich thinks that it is of Tertiary origin. Several smaller boulders, of from to 2 or 3 ft. cube, more or less worn, were dispersed irregularly through the gravel, which is scarcely at all stratified, and contains no fossils.

MIDLAND COUNTIES.

Dr. Deane and your Secretary have examined numerous boulders in the neighbourhood of Harborne, to W. and S.W. of Birmingham, between the Hagley and Bristol roads.

One hundred and sixty rounded and subangular masses of stone have been examined in this district. Fifty-five of these are clearly traceable to local rocks-Carboniferous, Permian, or Triassic; the remainder are of distant

origin..

Very few of these travelled boulders are in situ. They have been rolled or dragged off the land into ditches and by roadsides. Some, when the size has been convenient, have been used by the "nailers" of the district for hammering (or rather anvil) purposes.

Ninety are of the varieties of felstone so abundant in the Bromsgrove district. About half of these are of small size. Five are of considerable magnitude-5 ft. 6 in. x 5 ft. x from 2 to 3 ft.; the rest are from 2 to 4 ft. in length and breadth, with variable thickness. One of these felstone boulders (near Hole Farm, Moor Street, about two miles east of Hales Owen) is worthy of special notice. Its dimensions are 3 ft. 6 in. x 2 ft. 6 in. x 2 ft.; and it contains in one specimen the three characteristics named in a previous report as occurring separately in the boulders of Bromsgrove. A compact, almost hornstone-like matrix contains distinct included fragments and porphyritic felspar crystals. This specimen, therefore, confirms the view that these felstone boulders, which are so numerous to the west and south of Birmingham, as far as and beyond Bromsgrove, are portions of highly indurated ash-beds.

At Flavell's Farm, California, is one boulder of grey granite 2 ft. by 1 ft. 8 in. by 1 ft. Vein-quartz and quartzite constitute nine small and three large boulders; and one of these, found near Harborne station, contains included brecciated fragments of rock. The size of these quartzite boulders,

the largest of which measures 3 ft. x 2 ft. 6 in. x 2 ft., negatives the idea that they have come from the Bunter pebble-beds.

The general character of the boulders of this district is similar to that of the Bromsgrove district; but in the presence of granite, quartz, and metamorphic rock resembles the district north and west of Wolverhampton.

North and west and south-west of Wolverhampton, however, granite is very much more abundant than in the district west and south-west of Birmingham. The large boulders north and west and south-west of Wolverhampton are, it is probable, chiefly Criffell, or (more sparingly) Wigtonshire granite*; but there is Eskdale granite in the neighbourhood, especially about Bridgnorth.

The Welsh felspathic drift covers abundantly the west and south-west of the Midland tableland, while felspathic rocks from the Lake-district accompany the Eskdale granite, and are often mixed with the Criffell granite.

The boulders occur in two distinct positions (1) in the older glacial beds, (2) in the upper clay.

LANCASHIRE.

Large striated boulders have recently been exposed in the extensive excavations which have been made in the boulder-clay at Bootle, a northern suburb of Liverpool. The site excavated is intended for new docks, and extends along the river Mersey, being reclaimed from shore within the tidal range.

Mr. G. H. Morton describes for your Committee the position of these boulders, and gives the following section of the drift deposits which have been exposed continuously over many acres. The thickness of the various beds varies considerably according to position, and the middle sands and gravels often thin out and leave the upper boulder-clay reposing on the lower.

The whole of the subdivisions, 1 to 4, repose in succession on the Bunter Sandstone at that part of the section nearest the old coast-line.

The Lower Boulder-clay contains a much greater quantity of small stones than the Upper Clay. No large boulders were observed; but as the Lower Clay is not exhibited to any considerable depth, it may possibly contain some. The Middle Sands and Gravels consist of sands which frequently, by the great increase of rounded pebbles, become gravels, resembling those at Preston Junction, Wigan, Gresford, and Colwyn.

The Upper Boulder-clay contains comparatively few small smooth stones, but many large boulders two or three feet in diameter. Many of these are striated, and are composed of greenstone, but some are Eskdale granite. These large boulders possibly occur at an average distance of twenty yards from each other. A large mass of compact gypsum, about 4 feet in diameter, was noticed.

The sections described are still exposed at the present time, August 1876.

*See paper by Mr. Mackintosh, Quart. Journ. Geol. Soc. vol. xxix. p. 358.

CUMBERLAND.

Prof. Harkness reports that a boulder of Silurian conglomerate (the Queensbury grit of the Geological Survey) occurs at the village of Bothel, in the parish of Sorpenhow, North Cumberland. In length it is about 20 feet, in height 9 feet, in breadth 8 feet. It is beautifully striated on the western side. It is situated between the 400 and 500 feet contour-line, and has been transported from the north-west portion of Dumfriesshire, having travelled about forty miles from N.N.W. to S.S.E.

This boulder goes by the name of "Samson."

Prof. Harkness further reports that some fragments of Shapfell (Wastdale crag) granite occur in a field in the farm of Hindrig, near Dufton, Westmoreland, at about 800 feet above the sea-level. These have for the most part been blasted, and many fragments occur in the wall adjoining. Some of the blocks are untouched; but these are so imbedded in the soil that their size cannot be determined.

There are also several small blocks of this granite in gravels, which Prof. Harkness regards as Eskars, in a gravel-hole on the farm of Luhan, in the parish of Edenhall, about three miles east of this. Near the village of Newton Reigny, about two and a half miles west from Penrith, large boulders occur. They are so imbedded in the soil that their size cannot be determined. They consist of the Lower Silurian trap of the Lake country. Boulders of the same kind and of a large size are also seen on the east side of Newton Moss, which is a short distance S.W. of the village. The height of these Newton boulders is about 600 feet above the sea.

NORTH WALES.

Mr. D. Mackintosh contributes the following account of the boulders in North Wales. An account of previous observations will be found in the Quart. Journ. of Geol. Soc., Dec. 1874.

Between a mile and a mile and a half west of Llan-y-cil, on the northwest side of Bala Lake, the glacial striæ in several places average between 45° and 50° north of geographical west; and the boulders are of precisely the same kind as would have come from about the north-west or from the neighbourhood of Llyn Arenig. Both the direction of the stria and course of the boulders would cross Bala Lake at nearly right angles to its length; so that if the basin of the lake had ever been scooped out by land-ice, this ice must have come from the south-west before the period of the great boulder transportation from the Arenig mountain.

At the south-west end, and along the south-east side of Bala Lake, many of the boulders are not the same as those from the Arenig mountain, which are chiefly found on the north-west side; and they decrease in number northeastwards, suggesting the idea that they came from the south-west.

Through the gap immediately south of Moel Ferna, numbers of boulders appear to have found their way into Glyn Ceiriog, and cast as far at least as Chirk. Numerous large boulders have gone nearly due east along the valley of the Dee, as far at least as Cefn and Ruabon. The east and north-east boundary of the Arenig dispersion may be roughly defined as extending from Chirk by Cefn, Ruabon, Wrexham, Caergwrle, Mold, and the east side of Halkin mountain to Holywell, and thence in a westerly direction to the vale of Clwyd. This line nearly coincides with the boundary of the great 1876.

I

northern granitic drift. Both drifts (the Welsh and northern) have, to a slight extent, crossed the average boundary, and a few small Arenig boulders have found their way across the estuary of the Dee into the peninsula of Wirral, where they have become mixed with the very abundant northern drift from the Lake district and the south of Scotland.

The western boundary of the Arenig felstone drift would appear to run from the Arenig range in a N.N.E. direction as far at least as the celebrated Cefn Cave, near St. Asaph, where, to a slight extent, it has become mixed with the northern drift, and likewise with erratics probably from the neighbourhood of Conway. Few or no boulders from the southern part of the Snowdon range would appear to have found their way over the high tablelands situated to the east of Llanrwst and Bettws-y-coed, the Snowdon dispersion having radiated in all directions to short distances only, excepting towards the south. This Arenig dispersion is one of the most remarkable in South Britain. The felstone boulders from the Arenig range have radiated to great distances over an area extending from N.N.E. to E., and to short distances from E. to S.E.—that is, over the fourth of a circle. The boulders have found their way across valleys and over watersheds and high mountains. In most places they have wholly ignored the configuration of the ground, excepting where gaps in mountain-ranges have facilitated their transportation. A detailed examination of the surface-configuration, viewed in connexion with the positions occupied by the boulders, would seem to favour the idea that they could only have been carried by floating ice; but it ought to be observed that there is an apparent distinction between the large angular and subangular boulders which are seen chiefly on the surface, and those smaller and well-glaciated boulders which are found imbedded in the Lower Boulder-clay at comparatively low levels.

Among the Arenig felstone boulders, which are so remarkable for size, for the unexpected routes they have taken, or for the distances they have travelled, as to render them worthy of being preserved, the following may be mentioned:-(1) The Cefn boulder, a short distance west of Cefn station, near Ruabon, which measures 15× 14 feet, and at least 10 feet in depth; (2) the Maendigwychyn, or great immovable stone in the village of Eryrys, near Llanarmon (about 5 miles east of Ruthin), which measures 15 x 15 x 12 feet, and is situated about 1130 feet above the sea; (3) a boulder in a field near Bryn-Cloddian, north-east of Caerwys railway-station, and a few miles south-west of Holywell.

The direction of glacial striæ on rock surfaces in the eastern part of North Wales, as well as in the neighbourhood of the Arenig mountain, Corwen, &c., in general agrees with the course the boulders have taken. On the summit of Halkin mountain, in a quarry a short distance west of Holywell, there are well-defined striæ, indicating the passage of ice from the south-west; and in the neighbourhood of Llangollen, especially near Trevor (as lately ascertained by Mr. Morton, F.G.S.), there are several instances of stria pointing from

west to east.