As in the case of the porphyritic rhyolite last described, the quartz grains abound in liquid cavities with moving bubbles. The Peldar Tor Rock.

This rock is described at pp. 776, Vol. xxxiii, and 210, Vol. xxxiv, Q. J. G. S.'

I secured two specimens, one being in fairly good preservation, and not nearly so much decomposed as the majority of the fragments that I examined in the course of my walk.

The reasons that I have given for concluding that the Sharpley outcrop is a porphyritic lava and not a fragmental rock apply almost equally well to the Peldar Tor samples examined by me. The ground-mass is homogeneous in structure, and exhibits no trace, under the microscope, of clastic or pyroclastic origin. The rock has undoubtedly suffered considerably from the permeation of water, but I do not think the alteration thereby set up has in the two specimens examined by me entirely obliterated its original structure. Besides the porphyritic crystals, many of which are distinctly idiomorphic, the base of my best specimen contains very numerous micro-prisms of felspar in the slender elongated forms, and oriented in the manner, commonly seen in the later "generation" of felspars in typical lavas. Many of these are visibly triclinic. I see no reason to suppose that these minute idiomorphic prisms of triclinic felspar are of pyroclastic origin, as remarked above under the head of Ash, and there is nothing about them to suggest that they are of secondary origin. On the contrary, they have suffered equally with their larger brethren from the decomposing aqueous agencies to which the presence of secondary epidote and chlorite in the rock may be attributed.

The porphyritic quartzes in the rock above described contain numerous liquid cavities.

The presence of liquid-cavities in the quartz of such rocks as the porphyritic rhyolite, the volcanic origin of which has never been doubted, is an interesting feature, and it shows that we might err seriously were we to argue from their presence that the quartz fragments contained in clastic or pyroclastic rocks were invariably derived from a granite. Conversely the presence of fluid-lacunæ in the quartzes of the Peldar Tor Rock does not prove it to be of clastic or pyroclastic origin.*

* Professor Bonney and the Rev. E. Hill are engaged in a further study of this region, and of these Sharpley and Peldar Tor rocks in particular.

489

EXCURSION TO LAINDON (OR LANGDON) HILLS,

ESSEX.

SATURDAY, JUNE 9TH, 1888.

(In conjunction with the Essex Field Club.)

Directors: W. WHITAKER, F.R.S., and WALTER CROUCH, F.Z.S.

(Report by T. V. HOLMES, F.G.S.)

The opening, on June 1st, of the new line of railway from Barking to Pitsea having made Laindon Hills much more easily accessible than they were when the old line to Southend, viâ Tilbury, was alone available, this Excursion of the above societies was very numerously attended. About ninety Members were present in spite of the unfavourable weather, which, in addition to being showery, gave little promise of the extensive panoramic views mentioned in the programme, which result from the position of Laindon Hills as an outlying patch of Bagshot Beds in the middle of a London Clay district.

At Laindon Hills Railway Station the attention of the party was directed to the deep boring which was being made for a well in order to obtain a supply of water from some water-bearing bed below the impervious London Clay, which there forms the surface. Mr. Legrand, the gentleman superintending the execution of this work, was purposely present at the station, and kindly gave much information about this boring. From him we learned that the depth then reached was 444ft., and from his remarks, and from samples of the material brought up from various depths, we ascertained that the uppermost 342ft. of the boring were in London Clay. Immediately below the London Clay were:—

The beds below this depth of 366ft. were all more or less sandy. Mr. Legrand also stated that the septarian nodules found in VOL. X., No. 9.

36

London Clay were the only sources of difficulty to the borer in that formation.

Leaving the Railway-Station, the party turned southward and ascended Laindon Hills, whose summit is about a mile away. On reaching the top it went for a distance of some two or three hundred yards along the road, which ranges in an easterly direction towards Dry Street and Vange, to a spot where on the northern side there is a pit showing 12ft. or more of Bagshot Sand below three or four feet of loamy material. Here a heavy shower of rain fell, and Mr. Whitaker, looking down on the umbrellas of his attentive audience, discoursed on the geology of Laindon Hills and the district surrounding them. At the Railway Station (he said) they had learnt that the thickness of the London Clay was 342ft. Here the surface of the ground was more than 100ft. higher than at the station, and, as the beds were lying nearly flat, they would have to add some 100ft. to the thickness pierced at the station to obtain the full amount for the London Clay of that district. The sand before them was certainly Bagshot, and in all probability Lower Bagshot. If anyone present thought it Middle or Upper Bagshot he would remind that person that with the maker of that assertion lay the onus probandi, the natural presumption being that it was Lower Bagshot. Above this sand they saw a few feet of loam, and in the surface-workings at the top of the hill near the Crown Inn they had seen gravel, the exact age of which was doubtful, though it was certainly of later date than the beds before them.

The rain having ceased, the party then retraced its steps a few yards, and walked through Coombe Wood, reaching the road to Horndon-on-the-Hill, a few yards south of its junction with that leading to the old church. On the eastern side of the Horndon road the gravel capping the hill has been much excavated. Examination of one of the deepest of these sections-none of which are of any great size-showed, below pebbles in a very sandy matrix, sand like that seen in the pit just visited. Mr. Whitaker and Mr. H. B. Woodward were consequently inclined to think, that though there might be some ancient drift gravel (like that at Shooter's Hill and elsewhere) on the top of Laindon Hills, yet that there seemed to be no need to assume the existence there of other pebble-beds than those of Lower Bagshot age. It may be well to give here, in order to illustrate the character of the Lower Bagshot Beds of this district, the details of a section at

Brentwood, six or seven miles away, from Mr. Woodward's 'Geology of England and Wales,' p. 440.

This section affords a good illustration of Mr. Woodward's remark, on the same page as that on which this section appears that in sections near Brentwood the London Clay is seen to pass upwards into the Lower Bagshot Beds. Curiously enough, copies of the older map of the Geological Survey of the district (Sheet 1, S.E.), without Drift, show "Lower Bagshot pebble-beds," whilst the later edition, with Drift, shows "pebble-gravel" on the summit of Laindon Hill.

Few heights in the south-east of England equal Laindon as a spot from which the physiography of the surrounding district can be explained. On a clear day the spectator is enabled, by slightly shifting his position within a circle having a radius of about 200 yards from the crown of the hill, to see for a considerable distance in every direction. Eastward are the ridge on which Rayleigh and Hadleigh stand, the flats of Canvey Island, and the cliffs of Sheppey. Southward are the Kentish villages of Cliffe and Cooling, and the long dip-slope of the North Downs. Westward the most conspicuous object is Shooter's Hill, while the northward view is bounded by the high ground between Brentwood and Danbury. The broad Thames, besides forming an extremely obvious topographical guide, adds to the scene an element of beauty often wanting in extensive panoramic views, especially in this part of England. It was, doubtless, this possession of all the elements necessary to form a perfect landscape that caused Morant, the county historian, to describe Laindon as commanding the finest views in Essex, if not in England. And we have more unbiassed testimony in a work entitled, A Six-weeks' Tour through the Southern Counties of England and Wales' (Lond., 1768). This book, which Mr. H. B. Woodward had brought with him, and which was stated to be written by the author of the Farmer's

Letters,' was identified by a gentleman present as a work of the well-known Arthur Young. As might be expected, the writer treats mainly of the agricultural condition of the various counties visited, though he by no means ignores either the beauties of Nature or those of Art. His journey into the Laindon district seems to have been extremely unpleasant. He remarks that" of all the cursed roads that ever disgraced this kingdom, in the very ages of barbarism, none ever equalled that from Billericay to the King's Head at Tillbury." This road seems to have been not only extremely narrow but full of ruts of "incredible depth"; in addition, he was perpetually meeting with chalk-waggons, themselves stuck fast. Yet, he adds, "a turnpike was much solicited for by some gentlemen, to lead from Chelmsford to the Ferry at Tillbury Fort, but opposed by the Bruins of this country-whose horses are torn in pieces with bringing chalk through those vile roads. I do not imagine that the kingdom produces such an instance of detestable stupidity; and yet in this tract are found numbers of farmers who cultivate above £1,000 a year."

But his excusable indignation at the state of the roads did not prevent him from admiring the views from Laindon Hills, of which he thus writes:" I forgot to tell you that near Horndon, on the summit of a vast hill, the most astonishing prospect that ever was beheld by human eyes breaks almost at once upon one of the dark lanes. Such a prodigious valley, everywhere painted with the finest verdure, and intersected with numberless hedges and woods, appears beneath you that it is past description; the Thames winding through it, full of ships, and bounded by the hills of Kent. Nothing can exceed this amazing prospect, unless it be that which Hannibal exhibited to his disconsolate troops when he bade them behold the glories of the Italian plains! If ever a turnpike should lead through this country, I beg you will go and view this enchanting prospect, though a journey of 40 miles is necessary for it. I never beheld anything equal to it in the West of England, that region of landscape."

This paragraph was read out to the great satisfaction of the audience.

Though our journey of 40 miles from London to Laindon and back was quick, easy, cheap, and luxurious to a degree that if foretold to Arthur Young would have seemed to him wildly Utopian, the weather prevented us from enjoying anything that could fairly be called an "enchanting prospect," and, con