The Dorset County Express and Agricultural Gazette.
Dorchester, Dorset, England, 1886-03-23 00:00:00

LECTURE BY DR. MOORHEAD ON THE
GEOLOGY OF WEYMOUTH AND
PORTLAND.

On Friday, Dr. klawhead delivered • lecture on the
above subject, at the Working Men's Club,. in Conner.
ti.m with the Town Society. Mr. G. K i.liot, previ-
dent. occupied the chair. There was • fairly Lai.
attendenee &tempt those present being Dr. Childs,
I Genera/ Inglis, Major Cotton, Res. Stuart Churchill,
Major Wirlough. by Rev W. Lein; Nfessra W.
w
! e!, &erect, T. J. Tetlll4ol/12. A. A. Spline/ter,
A. Clarke, .1. Batchelor, W. P)e, T. Stone, Pickard,
and Padgett, the Rey. J. U. Barrudale, Dr. Carter,
and • number of ladies.
Lr. Nlooattran commenced by saving that as the
audience on the occasion of his reading • paper on
the geology of Portland, before the Weymouth Field
Club, last summer, was necessarily limited, he was
ofterwards requested to reread his paper before the ,
WWII Society, and consented to do so on condition
this the scope of ass paper was *Warped so as to

maraca the Weymouth district. Thus not iserely
une division, as was the cue in the paper he read at
Portland, tut the entire oldie.. ...ries of rocks a.
re*tew in the present lsr, which it was
hoped would in. thu -000.ur.t pow..n an
increased interest. llr. .l.n.rlwsd then 111111 P
wan* rereark• on the draws .1 rock, comp...mg
the earth'. cruet, and na..l ilea it wee the ...lite, a
member of the reowlary • of ...puma roan
which was particularly to etig.ge their attentein
that night. The oolitic iie.teui of roAs hal ae eh
sideteble distribution ii, ngland. They lamed •
sone aLsoit 30 mil.,, in wilth, whi.o e.t.a led from
Dorset, on the south-west c vist, t .41 .lie
north-eat. l'he oolitic a etem hid twee do id;nl
into three group., lower, i1..1,11., an 4 taptwr
all of which were well repreaated iii till: locality.
Before entering, however, into haal en.l.apeol
be mu.t take the opportunity of &eke..s ledging hi•
groat indebtedness to their esteented felowdown.
man, Mr. Damon, who.e adunreble work on tl,.
load geology had dune s much to pepularise the etiely
of that ecieno. amongst than. Br. Ihimou's valuable
hints and unvarying &weird his rarely.'
thanks. He could only repeat what he had said
elsewhere ; that the inhalaanto .4 the district mint
feet proud at having in their nielst a Fellow of the
Geological Society raw, knowledge of conchelogy A.
well as of geology had rendered hi, name familiar to
men of science throughout I kllPlmo..'. I).-
Nl.roehead then described the three group. .1 ...laic
rocks. Lower °elite, as .1...e10pel in tee. neighlyor•
hood, consisted i 4 biller',, earth. fonot niarble, and
onnihriali. Fuller'. earth, a., named from having been
employed in the operation .1 "fulling" fie the
ef removing grease fromw• ecan 11 n slid other tea.
fairies Was fonud in low cliff at 1•104100
Herring. iuonnliately I. lOW the 'outward
etation. It fortnal a clayey lel .4 a VII
colour, and Wan tn,,.t exclusively mote up
ot the shells .4 a .m ."I elongated fioeil oyster (o.tra
1,141.111,1i0) which WAS Chat:Wt. none .1 thin forni
eon. This deposit Was WIWI' expeted from laud.
ton Herring tor commereill as an &tenet-Int
supply, of superior qt. ility, hod tren obtained in
Kent, Surrey, and elwohe.... Fore.' marl'le WAS so
designated from ha. lug been tires otielied at tVytich•
wood Forest, in Olfanlshire, where the sea- had a
crystalline texture. Thie fermation oeculeed a I,ll'
side-ruble arra in the district. It was about two. toilet
in width, and exten.l.l from Itadipole ant Notting-
t.onr ..estri ~
westwards
Fleet, n
was considerably used fix bedding purponea The
only quarry exhibiting it in the district arm. that at
Langton Herring. (lariat/rash formed two narrow
zones running parall.4 along the northern and
southern borders '1 the formation last described. Ti.,
southern time, which wan *loan half a mile wide, coun•
menoal at Kadipote, by the I hxrcheeter-r....1, nm•
stituted the hill near the Spa, and formed the low
cliffs bordering the upper ettremity of the Back.
water :it thence travelled westward. by I 'hickerell to
li.. East Fleet. Th.. noithern zone appeared at
Nuttington, and then took a westward course by
Langton tO the W.' Fleet. There were a few
isilated patella of this formation, but they were
unimportant. Cornbraeh took its name from the
rubbly broken character of the stone composing
it, and aloo from the extrardinary fer-
tility at impartal to the soil in ch
growth of own-crash Middle oldie. comprised
Oxford clay and coral rag. Oxford clay, so milled from
it. forming the subaratuin uf the valley of the Lai.,
near that city, played a conepicuous part in our laal
geology. It commenced a little to the eaaward of
llani cliff, en the nortlvesowni nhore 14 the bay ;
formed the chief tortion of that cliff, then appeared
at Jordon Hill, by the Pi...ton Coaaltrlard station ;
and thence extended through Lielinoor tn kidipole,
where it divided into to-,, branch,. ,el.. of
its Confrw t.r Itl,lo4Way, anal then pro, sated due vest
to the nwanery at Abboaletry ; whil.• the ale r. after
binning the bed of the Weymouth ILlehriter,
by West liown and Mote Video to the Ewe Fleet.
Oxford clay, which sae noi .lly .4 a dark 1.11...
Was free free' sand or grit. It was couvpiently
,eatenaneiy tosel for making brick 41144...1M0 p 'Here.
the Malanf act to t. ul a. hich coos( 'tut. d . use .4 the •t aide
tudizarisa of this diatriet. It contain...l a few oliwet
which, whether regarded (coma scientific or Poe" •
point of view, isoy-owd coneiderable inter.t. The
find of Owee that deo,, ed nen, pens iron pyritee,
stabalance large ly diffeed in this foritattion. aod
which was a eh...nivel comp ailed a...neighs': of tie
thirds iron and one third .41.1va. This pyrite.. was
an article .4
dation of green vitriol All,l solphurie avid new
pounds or carbonate .4 eon and oiligeirettal
hydrogia, formed Ihr the decomplaition of the
pyrite,. throng,' contact with rani water. were the
chief conotituent 4 the mineral water found in this
iwichlsoirhierd. at the juncti tttt of the rornlwash and
oxford cley—the Kedipole Spa. Tbe prawn,, of
iron in the water there WA. i11,i1C314,1 I.y th.• nasty
dep atm funned eu t of tior
containing it, whil.t ti..• alphurethel hydrogen
Was readily frentnin. oy its chararteristie .1-011 r.
Ti,,' amount .4 the gna, however. varied eouider,
aldy ; thio variation was doubtlea determined he
the rainfall. Ife mentioned this int...mit...et
evolutim of the gao loyalty. it was .4 interest, as it
would probably ',call to mind the Pail .4 Iletheoola.
at Jeruaalem, mentioned ii. tlw Holy Scriptures. Of
thi• pool, it was record.. 1 ire the S erred Narrative
that it was much resorted to by the chronic inaalids
I.f the Holy City, inelticling "a great itioltitiele of
impotent folk, id blind, halt, withered," who had to
"wait for the tllotilla if tla water," "for an Anzio
went down at a certain seaem th-, pool and
troubled the water ; wh...ever then tir.t, after the
troubling of the water, stepper' in. Was made whole
of whatever disease he had.' A a commentatoni
on thie peerage, there we, a general calumets of
opinion that the Pool of Betheeda was • natural
mineral water, which owed its healing virtue. to the
flatiWolls element with w hub it Was periodically
impregnatml. but that the nature of the i.tn• was
uucertaia. There were four In-.. KANN (011114 in •park.
lieg mineral waters hydowen. carbolic
aid, nitrogen, awl oxygen. Of these, the three lut
named, according to modem science, when optilied
externally to the 1..1y, hol scarcely any appneable
therapeutic action ; whilst eulphiw, ifl its senate
forms, had bra rec.- iguiral from the earth at tinea
a remedy of undoubted efficacy el tho trear.perg of
chronic rheum/Alain and allied a1t....ti0n,. When
to this be added that the Inicatone ("mile •
ing Nlonnt Nfoi bah and Nfoont Zion woo ly
regarded as oolitY. mel therefore -imam' to
the formation. in the Weyeeestli diotriet, re
was strong iww, IWIVP t,PIPItre that the Pool of
Bethada was, like wir 1410, a radiant,. us
and probably eh ilybeate npring, owing its curavve
propertiee mainly to the ga. with which it WAS ppri..di
cally charged. If the. view wen, correct, it would he
evident that all who entered thel.el while it gay an a
...Ate ligittiti.at by the ga., however great the
moldier, ineild Pier,. e Irenefit Iran its hailing water..
Leaving this digression, Dr. Mewhead referred h.
another object .4 intern." found in Oxford clay, sir.
selenite or gypeutn, Os erynallised sulphate .4 lime.
Selenite existed in the form of a rhiinhoicial crystal
which could lw readily reparated inti, thin plate.,
that, owing to their transparency. Were employed for
optical purply.. When calcined, gypeein wan con' !
.ertecl into that well-known white powder called
plaster of alabaster, and in this suaturphoias
Irate was largely employed ita the arts for making
caste, statuary, and etherobjects. The concretionary
nodules, technically called ...Marva but popularly
termed " iaelding " turtle stones," front
their reseniblann., when poli.hed, to the carapace of
a tortoia or turtle, likewise found in Oxford clay,
were oleo alluded to, and their comp.sithin and cause
of fonnation touched mon. TAPS. wrialria were nigh
apicuangy displayed in the cliff of Oxford clay facing
the Backwater, at a short diotance from the
Weymouth railway station. They were not confined
to Oxford clay, but were abio faia in Kimineridge
and London clay. They appeared in the Wilderness
of the Tranptation, near Jernsudern, and were .11p-
p...1 by Canon Farrar to have been the igomes
pointed to by Sista when he said to Christ, " Corn•
mand that theme *einea be made bread." Coral rag,
the next constituent cif middle oolite, prevented
itself in two nearly parallel ridgee running from ...ant
to west, and nominee...l a notable feature of the
geology of the dietrict. On the mouth. it formed the
N'.the, Clearmount, 11.111.-1.1. and Wyke Hill. On
the north, it commenced in the cliff which extended
from Bing.tead to Osminirton 111116 t thence, after
considerable displacement of the ',trate, it proceieled
westward., forming the basis of Black Hook Cliff,
and alio .4 Ham, .fordan, and Lorton hills, until it
reached liroadwey, when, it might be seen in the
oer railway tufting. From this leint, it Hein cm.
'limed its coitrw, until it reached the West Bay
where it terminated a little to the east .4 Alibotehury.
Castle. St. Catherine's Chapel, not far from the
village of Ahl.asleiry, was eituated upon a hill .4
coral rag, while the Ilche.ter Garden, owed their
luxuriance, in sone- meas...., to the nhelter afforded
by bale'• hill, which Was VottijalaWl of the same form-
hese. Dr. Moorhead then went into particular. of
the three group+ into which coral rag, or corallian
(Ade, as it should he deeignated in this district, wrie
sub-divided, viz., Lover caleareoua grit, coral rag
Ipruperhand upper CalnarlioUS grit. The lower and
upper grit. conowted of 1.10 of ....Ir.-pained lime.
atone, alternating with thiek layero .4 sand or clay.
It was the pree-nee of the late, which hel to the
disintegration .4 the cliff. surrounding the soot,. •
extremity of Weymouth Ray. Under the combined
effect of wind and rain. the ioft IllatatfLat leaf
gradually removed. mud the overlying rocks became .
ono...nosed, and wet,. mecipitated opon the leach
benath, as migla be seen at Bincleav a and at
Sarubifoot Cootie, and alio near Osieington Mill. and
Haul Cl.lf, Th• middle group of the " coralliatiwas perh.spa the "
snfles. It was io,.st tu.i.ti; d.v.ioved
terestvng a the
tyoica
i 4
midland cantina, espeoielly in Wilts, where the
remain. v 4 fossil coral. conotituted masses of ruck
varying ie thicknees from fifteen to forty fat. It
therefore, jintly designated there coral rag'
but toward, the northern extremity of the write. -
lone in Yorkshire and also the eoutheni in Ikea', I
corals were comparatively rare, their place being
occupied chiefly by fund 1110Misal or slw.Ufiab. This
variation was probably attributable to the shallowness
et
.tbe sea in which the deposit was formed in this
=boarbood and in the north, the drainage of fresh
from the land being Ivrea to the coral
enophyte. But, thongh rare, corals were not altogether
absent from this district; he was enabled to exhibit
representatives of the two leading foal peers—one •
branched coral (theereimilia), and the other a wade
....ocera""alf ratldlia.ingo 2.(tvihoitetamhoev4nierirnas,
atreatlnvai;igoitaigtouirtnihoeinc:amrullF....4r.Ffifirac.fhlt.h.;:annnln7vtliite."ozhi7iwe.
Moorbsad brie
d.,tributsen of
world .n the present
d'w.
e:Beliyia......;trwaz roniniinuilauei:::b.iteilit:istthhtehurviinr...u;clure and
corals were shout exclusively' confined to tropical
ere
ilantildhedei"Atiranalz:edtreiCPtbewheiitfiihrC
the excel'
I hey
develornent was supposed to be due to the warmth
'of the Gulf Stream. Existing corals presented them-
selves in the four following form. : —I, Atolls or
lagoon islands; 2. encircling reef.; 3, harrier reefs
and 4, fringing reef.. Atolls consisted of a circular
or oval strip al land, varying in width from a quarter
to half a mile, and a lagoon or basin of still I
water, having dia7ol:ol7lreel 000 10 thirty