J. M. BLACK ON AN ERUPTION OF !{OUNT VESUVIUS. 265

safe descent, but it would be doubtful to say what wouldhappen in descending with this velocity if you were to st rikeaga inst a projecting piece of lava embedded in it. P ossibly, andvery probably, you would lose your equilibrium, and be th rown for­ward, and arrive at the bottom of th e descent in a very differentmanner and conditi on to what you expected at sta rting. Onarr iving at the base of the cone, I made my way across th e lavabeds to the Hermitage, afte r a toilsome trudge, and th ence drove toHesina, and took train to Naples.

3. ON SOME NEW CRAG FOSSILS.

By ALFll ED BELL, ESQ.

EXCURSION TO PLUM STEAD AND CROSSNESS.

JULY 5, 1873.

Directors-HENRY WALKER, E SQ., F.G.S., W. WHITAKER, E SQ.RA" F.G.S., AND FRANK E. H OUGHTON, E SQ.,

(Report by Mr . Wa lker).

Th e party, which included a number of visito rs from the W ork­ing Men's College Fi eld Club, left th e Cann on- street RailwayStat ion for Abbey W ood by the 3.2 p.m. train. Th e principalobject of the excur sion was the inspection of th e sunk forest- bedwhich underlies the marshes at Plumstead, and is visible at lowti de in th e river Thames.

On arriving at Abbey W ood, the company proceeded across th emarshes, a distance of two miles, to th e ground occupied by theMetropolitan Main Drainage W orks at Crossness, admission havingbeen kindly g ranted by J. C. Bazalgette, Esq., C.R At this spot,where th ey were met by MI'. H ough ton, th e resident engineer , theintention was to take boat and inspect the submerged tr ees, whichare exposed at low water, on th e Essex side of th e riv er, imme­diately opposite Crossness. 'l'he tide, had, however, alr eady risentoo high for this part of the programme to be carried out, butfortunately another exposure of th e forest-bed had been provid edfor th e occasion. By th e dir ection of Mr. Houghton, th e marshhad been opened for a depth of eight feet; at this section th e buri edland sur face was well seen.

2G6 EXCURSION TO PLUMSTEAD AND CROSSNESS.

The section was as follows :-

"

"

"

"

2 feet.

3 "3 "

Alluvial deposit.Yellow ClayBlne Silty Clay.Peat bed, with stools of trees still rooted

The succeeding deposits are thus given by Mr. Whitaker, in thedetails of the Crossness Well-boring in the same marsh :-

Peat with remains of trees. 6tfeet.Dark-grey Silty Clay Ii "Thin layers of Peat and Clay, with

decayed wood full of phosphate ofiron Ii

Dark-grey Silty Clay 2iSilty Sand . 2Valley Drift and Oldhaven Beds (1). 49Woolwich Beds

The Members then examined the peat-bed for themselves.Among the stumps and trunks of trees (some of which were ofconsiderable size), th e oak and alder were recognised, a catkin ofthe latter being remarkably well preserved. Mr. Houghton ex­hibited some articles of furniture made from oak taken out of thesemarshes during the excavations for the Main Drainage Works.

The forest-bed has a considerable range. "From the bed of theriver (in which the peat is found by soundings) the forest passesunder the marshes of Kent on the one side, and Essex on the other,where it is concealed by the overlying alluvium, and is only revealedby excavations. The same forest was found under the alluvium inexcavating the docks about the Isle of Dogs, and in excavationsin Lambeth and Wandsworth marshes.

" During the excavations in Plumstead Marshes for the SouthernOutfall Sewer in 1862-3, the forest bed was well exposed.

"Mr. Searles V. Wood, Jun., F.G.S., writes:-

, I followed the forest from Woolwich Arsenal to CrossnessPoint continuously. Hundreds of trees had been dug out, andwere lying on the surface, and we saw some great stools rooted inthe gravel. The depth of these stools below the high water markof spring tides in the river was about 25 or 30 feet, the marsh sur­face itself being in places many feet below this spring tide level.'

* " Memoirs of The Geological Survey," Part I, p. 460.

EXUURSION TO PLUMSTEAD AND CrOSSNESS. 267

, At Dagenham Docks, on the Essex shore, the trench was openBorne four or five years since, and the section of the forest on thegravel exposed.. There was a heap of the peat hard by, and out ofthis you could pick sprays and leaves of oak as fresh as out of anyditch bottom where they had only laid a year or two.'

" The existence ofthis Forest bed in the Thames is considered byMr. Wood to confirm his own original views as to the history of theriver. Mr. Wood believes that 'The Thames had formerly nooutlet to the area now known as the North Sea, and that thedrainage from Middlesex, Essex, and their adjoining countiespassed into the Weald, by channels of which three can be traced intrumpet-shaped openings. One of these is at Merstham, nearCroydon, another is the valley of the Darent, and the third is thevalley of the Medway, the present eastern ontlet of the Thameshaving been effected at a very late period.' Mr. Wood contendsthat 'The Thames is qnite a modern river, and has no connectionwith either the great gravel sheet or with the Cyrena brick-earthsof Grays, Erith, Crayford, Tottenham, Homerton, Shacklewell, &c.;that, in fact, it came into existence as a line of drainage fromLondon to the North Sea only after the elevation and desiccationof the Post-glacial sea-bed of the Weald had put an end to thedrainage from Middlesex, Essex, Kent, &c., passing into that area;and further, that the origin of the Thames is coeval with that of theNorth Sea, which was principally a land area when the Thamesgravel was deposited and the sea was over the Weald. The samedepression which gave origin to the North Sea during the eleva­tion of the Weald caused the old land valley through which theThames now runs east of London to sink, giving rise during theprocess to swamps in which peat accumulated over the forest, untilthe drainage, finding its way to the sea by this new outlet, thepresent Thames river became established. Its waters in theirnatural unembanked state, by depositing the marsh mud, thensealed up and preserved the old land surface, Submerged landsurfaces of this period occur at many points of the English Coast,the depth at Grimsby in Lincolnshire being as much as fifty-twofeet below high water of Spring tides.' (Quart. Journ. Geol. Soc.,Vol. 241, p. 157.) The stretch of this forest-bed in a continuousline across the valley bottom between Kent and Essex, inclusiveof the bed of the river, proves,' Mr. Wood contends, 'that what­ever difference in elevation there may have been, no land drainageat all approaching in volume to that carried by the Thames, still

268 EX CURSION TO l'LUMSTE AD AND CROSSN ESS.

less th e more copious snow and rainfall of the epoch of the forest,could at this epoch have flowed through the valley now occupiedby th e Thames east of London.'

"The earliest account of the submerged Forest at Plum steadseems to be that given nearly 150 years since, by Capta in P erry,the famous engineer who repaired Dagenham Breach, who describesthe fossil trees as 'moor-logs,' th e name gi ven by th e Th ameswaterm en. Captain P erry gives the species of the tr ees-hazeland willow-and the mode of their occur rence. A little later (in1710 ) an account of the forest as revealed at Dagenham appearedin th e ' Philosophical Transactions ' from the pen of Mr. Derham,who mentions th e names of th e following places where he tracedthis same subterranean forest-Dagenham, Hav ering, Rainham,Wennington, Purfleet, West Thurrock. Both. Captain Perry's andMr. Derham's accounts are quot ed in detail by Dr. Buckland,(Trans. Geol. Soc., 1817, Vol. iv.)

" R emains of reindeer, elk, and ox are found to-day in th e forestbed associated with flint implements of the Neolithic period.v'"

Having been furni shed with th e above details, the company wereinvited by Mr. Houghton to inspect a collection of objects takenout of th e peat, and some coloured diagrams made from personalobservation of the Main Drainage excavations across Plumst eadMarshes in 1862. The alt ernation of horiz ontal vegeta ble bandswith silty clay was well shown. Some interesting and instructivefacts bearing on the origin of sunk forests in river est uaries weregiven by Mr. Whitaker, who did not agree with Mr. Wood'saccount of the Plumstead forest-bed.

The Crossness W ell--boring was th en visit ed, it being understoodth at the work suspended in 1869 is about to be resumed imme­diately. Up to the present tim e the boring has descended throughthe following deposits :-

F eet .Alluvium of modern Thames, overlying a F orest-bed

with Mammalian remain s (Post-glacial) 22tValley Drift and Oldhaven Beds 49Oldhaven Beds or Woolwich Beds. 16

Carry forward 87t• The paragraphs here quoted ar e from a circular specially prepar ed for th e ex­

cur sion by Mr. Walker, copies of which were distributed among th e Members.Th e circular also contained an original section drawn by Mr . S. V. Wood, jun.,extending from Bostol Heath across th e Thames at Crossness, and as far as Ri pple­side in Es sex, showing the position of th e sunk forest-bed, and the supposed faultat the Crossness Well.boring.

EXCURSION TO PLUMSTEAD AND CROSSNESS.

Brought forward.Woolwich BedsThanet SandsChalk.Upper GreensandGault Clay .

Total

269

8T~

1432

646i12

148

940

" There is every reason to believe," says Mr. Prestwich, "thatthe base of the Gault will be reached by prolonging the boring an­other forty or fifty feet."

Cores of the various deposits obtained during the boring wereexhibited by the Engineer, and inspected by the visitors. Thebearing of the enterprise upon the question of the proximity ofthe Palesozoic rocks to the Gault was explained, and particulars ofthe results of similar borings were given, including those atKentish Town, Harwich, Ostend, Calais, Hames (near Calais),Valenciennes, Flines Nord, and Mons. The company then re­turned to Abbey Wood Station for town.

EXCURSION TO MALVERN,

JULY 21ST, 1873, AND FIVE FOLLOWING DAYS.

Directors-s-B: B. GRINDROD, Esq., M.D., LL.D., F.L.S.,F.G.S.; the Rev. W. S. SYMONDS, M.A., F.G.S.; and the Rev.ROBERT DIXON, M.A., LL.B., F.G.S.

(Report by J. Logan Lobley, P.G.S.)

The Members having assembled in the Museum of TownshendHouse, Dr. Grindrod described his well-known collection of therocks, minerals, and fossils of the Malvern District. The paleeonto­logical collection, although a very large one, consists almost entirelyof palaeozoic fossils, and is arranged in stratigraphical order. Thestudent is accordingly at once made acquainted with the character­istic species of each formation in the district. Above the casescontaining Ccelenterata, Echinodermata, and Mollusca, each of whichgroups is abundantly represented, a glass-covered case extendsalong the whole length of the room, and is filled with, perhaps,anunrivalled collection of British Trilobites. Most of the specimens