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Capel Curig. June 19th Sunday 1842

Examined course of torrent of Conway above the C. Curig I find slate—rock worn into circular not always quite vertical: deep cavities where a flat—table whether inclined a little against or with the stream, & above which in floods there will be eddies. Also when inclined steep shoulders project & when in flood there must be eddies, rocks deeply worn.

Found one beautiful deep basin & joining to it another quite circular smooth one, with mouths of both deeply worn down. The bottom of the smaller one, had a smooth sharp smooth conical projection of stone, (like but sharper than bottom of wine bottle) which cone is as connected with sides of cavity by a much curved lower sharp little ridge – bottom of hole was like inside of last worl of uniscle.

[sketch] Eddy in floods

there was sand at bottom & in another smaller one in which I could only just get [ash] after picking out many pieces of stone, the bottom matter

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was sand & here was a point these facts show that only sand or small stones are wearing agency, for big stones wd make concave bottom, & that motion must be revolving & not like waterfall— The position of infinite holes showed me that mere eddies produce whole. I remember in severn eddies keep constant.—

In case described in last page the true fine cavities had each large mouths worn down & close to them there evidently had once been three or four, how worn away into a spoon-like valley at right angles to stream. In other case eddies have worn back rock in hollow almost parallel to stream— Then great circular hollows with one side worn away are clearly produced by eddies for I saw one now with stream low & powerless beneath water, in spot in which during floods must be strong eddy. Now hardly any eddies for stream has worn its bed in accordance with its course.— Proved hollows produced without waterfalls=

[2v]

Walkers' map

Capel Curig Lake 580 ft above sea

Flint — Pebble could not get on Glacier

(Shells transported same way)

[Darwin's personal journal entry: "& on 18th to Capel—Curig, Bangor, Carnarvon to Capel-Curig; altogether ten days, examining glacier action".]

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Capel Curig. June Sunday 1842

In mouth of valley north side face of rocks sloping steeply to S. (near bottom of valley old road / scored vertically down as if very heavy stones had slowly slided down.

Boulders of foreign rocks on the flat stretch between the little valleys. on the shoulder — mountain on north side of mouth of Capel C. valley.

Monday [June 20th]. Mountain N. of two lakes lower part grey—wacke — small metamorphosed upper part all schistose slate – worn into shoulders — appeared some of them on same level— immense number of boulders projecting flat points in the case in small groups & rather in lines – especially on a slope facing Snowdonia — rock hard compact [Insertion:]= a porphyritic greywacke/ commonest kind= — coarse greywacke. feldspathic rock— brecciated porphyritic rock & true porphyry.—generally rather rounded, not scratched in this case perched on shoulder of slate — one to 3 yard square — one above 26 feet long 12 wide depth unknown – another

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18 ft long — immensely numerous — but easily overlooked from general similarity to surrounding mountains. Some May lie on summit of crest between this valley & a small steep one whi descends into valley of Conway, a little way before on below Ogwen lake. = no moraine on hill = Isld think at least from 800 ft to 1000 ft above Capel Curig lakes. =

In Walkers' map Capel Curig lakes 380 ft above sea

Tuesday (21st) Examined all the bos-formed hills round Capel C. scored & smoothed with many gigantic boulders perched on the summit of nearly all of them, & in imperfect circles round flanks of some. This well exemplified— Many rocks wil not score.—

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Went to Lake Idwell (?) The mounds of rubbish strewn with gigantic boulders (can see superposition) near division of waters between Conway & Ogwen by ascending them are seen to form an irregular sweep as if they had formed N. Western moraine of the great glacier wh. must have descended in NE line from a great valley of the Glywdr mountain before coming to them the right hand of road strewn with innumerable boulders perhaps the terminal moraine.

— bos-formed rocks on flanks & all round Ogwen, like all round Capel—Curig lakes (Hence these lakes not filled up)

Mouth of Lake Ogwen "perhaps vomitory" attention thus called— 10 to 20 yards from bridge— bosses far better scored than any I saw irregularly some of the zig—zag, these on flat surface on a steepish slope connecting two such flat horizontal scores— best scores I anywhere saw — an appearance of fine striae at right angles. I believe produced by the grinding of laminated slate, the softer layer yield

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most easily.— masses few feet square of slate with their summit worn & scored project.— as sculptor leaves lumps unworked on perfect figure – metaphor perfect if sculpture was reducing large statue into very small — observed it at bottom on opposite of valley in several places a character different from any ordinary atmosphere a aqueous denudation.— Whole barrier N. of Idwell by ascending it every mass is bos-formed & when a flat gulf separates the bosses their steep sides are scored in slightly descending lines — rocks bad for scoring some from ingress as the nodule quartz rock & some from numerous planes cleavage fissures & stratification — few perched rocks. (when glacier have met rocks divided by many planes of cleavage seems to have disturbed & twisted them & not grind them) — whole barrier from summit bosses on side to bed of valley perhaps 500 ft all worn to close to very bed of river.

Walked along west side of lake [CD gets E & W confused here – he means east side] rock smoothed & scored under water of lake on west [E] side

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at farther end — appear mounds of rubbish by ascending them. they are found linear only bisection by torrent three lines & trace of a fourth— corresponding but much less developed ones on eastern side.—

—The one nearest lake can be traced some way up mountain side & deform space but held covered by glacier namely that enormous perpendicular black face of rock at S. end of lake admiration of travellers — the outer line most striking = about 10 to 15 feet rises from hill side. — all strewed with gigantic boulders considerable height some 100 yards in length each line diverges more & more at its outer end — must be ascended. —most striking external glacier. external crater — unequivocal moraines = extreme pleasure to those who have read Agassiz &c = thanks to Buckland =

These lines mark retreat of glacier, in its last stage— entering the glacier must have extended at far greater height for I found bosses & scored

[7v]

The Idwell moraine far smaller but far more perfect & define limit of glacier, then the

great one mentioned by Buckland. Eleven years ago, in spent day here saw nothing nor shd have if not pointed out. — therefore this notice no rock what I should call "polished" but smoothed

Glyder Idwell. — valley of Nant Francon Buckland says dome shaped bosses near Penrhyn slate-quarries

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rock as above the moraines — The moraines of that day could not have rested after retreat of glacier from steepness of hills.— From height of lake, & steepness & height of mountain all round glacier existed after other had disappeared, hence these moraines are so much more perfect than any others.— immediate barrier of lake where river escapes a low mound strewn with one threads over way through boulders, when I could find no rock in situ — possibly a terminal moraine in one of its stages. —

Due W. of exit end of lake, a steep gully descends with rock in bed (hard to see from coincidence of cleavage & moss) scored vertically & worn into smooth slopes vertically down. — when glaciers at head of lake formed the inner moraine this formed a small separate glacier— & at its foot little rush plain 100 yards across surrounded by semicircular low mound of rubbish i.e. terminal moraine, breached by stream mounds cast on bos-formed rock worn by glacier in it greater extent.—

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60-80 yards west [east] of exit of river — a gigantic boulder broken into 4 tabular masses they two rest on their narrow edges upright the two lower ones have fallen over & rest on neighbouring great boulder. —The two upright plates stand transversely on gentle slope in which they rest.— The fragments are so far a part this immense mass must have been thrown with force where it now stands, but not rolled from neighbouring precipice otherwise plates have been thrown over — crevice of ice fallen though.— example for a stranger.=

I have said rock bossed (this structure required practice) at base of barrier about 200 ft beneath Lake Ogwen— no beds of pebbles have not subsequently covered by sea.— yet sea at Faban 1000!! ft if diluvial wave valley form straight vista sea [illeg] Anglesey. No lateral moraines for when glacier high they could not have been formed. bottom smoothed ⸮ from River? with few immense boulders of no transverse moraine odd! effect of barrier of rock?

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Ascended to Lake Bocchlwyd (?) E. & high of Idwell, bos-rocks poor. No moraines possibly obliterated by falls of stones.

All way down Vale of Francon fine boses of rock — no terminal moraines — peat-bed. covered up? —

= Bethesda, ascended Moel Faban & hills beyond — no trace whatever on it if glacier action— hard schistose rocks project in uneven manner (good contrast) from whole surface — strewed with slate little rounded fragments – Falkland Isd lifting of ice?

On flanks undoubted large angular & rounded boulders— here no evidence of glaciers & position by unfamiliar — isolated & out of passage from central mountains by sea.—

Summit strewed with boulders of crystalline rock considerably rounded like high ones of Capel Curig. I presume distant boulders at least differed from rocks in which they lie but the hill in divisively composed with similar

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rocks to many of the boulders. Neither on this or the surrounding hills any gravel &c like Shropshire & Staffordshire beds. ⸮ surface shells [river]— I saw some fresh one cockles at very base of hills =

At very foot E. of lower end of Bethsida, in a large slate quarry covered with bed of till, with boulders no trace of stratification, from 10 to upwards of 30 ft in thickness— till like S. America.

White earth — from a very even, sloping cons little plain — evidently levelled by water, sea =

In other quarries close by N of it & nearer village same till has been quarried for extensive spaces slate not bossed beneath it but found in neighbouring pap of greenstone smoothed & scored by icebergs?? — In further end of Bethsida I am very, & some way up E flank I am doubtful about the bosses entering on whole

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far less bossified than at Capel Curig & Ogwen &c =

In the till the boulders in large proportion are smoothed & most distinctly scored —so several say from main head to great size commonest say 1 to 4 ft square

Its scores sometimes irregular & crooked, generally parallel in one very large one all exactly parallel on the one large exposed side. — in many smaller ones, scored on both sides — in one large one the same thing occurred & the scores parallel on the opposite sides 1 to 2 or 3 ft square — in a conical one 4 ft long 3/4 of circumference with parallel striæ — wh some stones scored only on the side— whether stones are more generally scored on one or both dull sides cannot say for impossibility of turning any except the smaller ones. O thick dirty on lower sides — in small (a large a big headstone which are elongated, scores parallel to longer axis, showing adjacent neat.— In three

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large stones embedded with one vertical side exposed two of them scored horizontally & one obliquely — Stones could not have resisted scoring when many standing on their own base & in the earth boulders could not have been scored on both sides.— therefore not scored in till like Maclaren's boulders — Delivered by terminal moraine into water, probably sea.— Particularly remarked perched boulders not scored at Capel Curig, &c or on Moel Faban = no tails of Diluvium there =

Saturday. Below Bethesda certainly far few, if any well characterised boses; very many irregular ordinary hillocks of rocks — saw till in other places

­—Bethesda must be highish (N.B. highest part of Holyhead road 1000 ft above Ogwen?)

also pla sloping planes & some of the till partly stratified irregularly with

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more gravel — also still lower beds of gravel —

Between Bangor & Carnarvon flat-bottomed valley with isld or peninsula hillocks & terrace-like ledges with till & gravel — undoubtedly sea apparently few boulders saw one in till — hillocks not bossed.

Sunday Carnarvon to Moel Tryfan – undulating boulders plain walls composed of boulders some large some appear scratched — near Carnarvon slate rocks & crystalline hillock not bossed; former covered with 10 to 20 ft of till —

Moel Tryfan — isolated hill in front of Mynydd Mawr not in path of bow glacier rocks when exposed & when covered up not the least bossed jagged — slate & a conglomerate.

— numerous slate pit on flanks, — these show

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the slate covered by a few feet of slate fragment sometimes partially retaining position,

generally chaos & then 2 to 3 feet of earthy matter with slate & of partly-rounded (hardly any quite small) pebbles of very many rocks crystalline. North Wales porphyry & true good granite; also with boulders angular & rounded & angular— boulders large & numerous all round summit of hill of many rocks did not see one large one of granite — not scratched or at least only one or two. Mostly well rounded some quite angular – not brought by glaciers ∴ by icebergs, hence state of surface of slate wh appeared very odd at first to me.— On East side (4 or 5 ft in places more chaos of debris fragments of slate)

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(inland) side of hill, bend 10 ft 20 ft thick of gravel, river sand, yellow, boulders numerous irregularly decidedly stratified, & clayed-sand not improbable for shells looked most carefully there & all round hills could not find any = pebbles of chalk flint & white granite, decomposed close to summit of hill, wh I suppose is 1300 to 1400 ft high =

I shd think large proportion of rocks boulders from Wales. From the state of slate here &

absence of Bosses below Bethesda. I argue that icebergs do not tend to form bosses =

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Sunday Evening A slate rocks S. side of lower lake finely scored & excessively smoothed = slate rocks show well low level on banks of Llanberis only 310ft = softness of slate contrasted with other rocks favourable =

All hillocks bossified about Dolbadarn tower.

Monday —A slightly projecting shoulder, where valley slightly turns, W S W E. N. E. of upper end of upper lake, vey precipitous, bossified — This structure reaches to judging from the other mountain nearly 1000 ft above lake, at the upper limit a perched boulder

Just around the corner & within (going up valley) thin slight shoulder the ice has grated in most wonderful manner — no doubt visible 60 or more yards off some furrow 2 miles across — not formally a rough schistose feldspathic rock, for scoring— scores nearly parallel, horizontal, but on some two nearly perpendicular smooth faces, (where best exemplified) the ice from resistance seems to have tried to have passed [throug] narrow gorge westward & in = scoring both sides =

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The plain of Carnarvon very extensive bo slope to sea & to main valleys, good "till" in one place.

Bossed rock at least as far as just below lower end of lower lake.

(Describe as if descending valley & introduce account under head of best furrows =

[Diagram]

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this passage has risen at taking one best case, & laying it on paper at angle [sketch]

In another steep face only 20 yards (up valley) off, but facing in different direction at

nearly rt Ls. scores descend, as much as they ascended where measured – 50 feet

above the faces hill jagged slate. No signs of bosses on scores on boulders— limit of ice most clearly marked

[Right margin:] Marked contrast

In a hill with reddish top, SSE of [Victoria] Inn S E N.W of former hill in same range —

The ice has swept from NW  SE & tried to get westerly over its SE show slope, the

(i.e. ice not risen so high, with power of bossifaction) summit of this hill is not bossed or scored though rather lower than scored faces of former hill; & the line of bossifaction can here be traced likewise pretty distinctly. This hill

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[Diagram] 19º upward score Llanberis face running ab W by N. & E by S.

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has been protected from S E from N. W.  flood of ice by the former.

On summit however fragments, apparently not from a distance, have been turned over & placed, as they could have been a prominence of other rocks as if ice had passed over once or twice with great force, sufficient to bossify.

The whole SE slope of the hill (ending a remarkably range) is scored with lines pointing SE, & in manner showing the ice must have expanded & turned westward.— to remarkable amount & inserted itself in all the gullies between the bosses in the SE gentle slope.

— Perhaps Dobbadees hillocks have deflected westward [by] the ice.

[sketch]

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About Capel—Curig say ice extended 800 ft judging from boulder & smoothed rock to quite or nearly the height.

Till of Bethesda so like till of Fuego that without proofs of inundation I must believe tranquil deposit.

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In the valley entering between lakes from SW the rocks are do not appear bossed at nearly such high levels as above described, but the lower parts appear to be so thus on sides of valley above Llyn Dwthwch on west side some bosses under turf almost polished = In valley close East of this possibly lateral moraines.

I have no doubt ice descended from Lake Ogwen to Bellws & from above it to Llanwst

Dr. Buckland says there are marks = so [Wales] isld of ice =

Capel Curig side two or 3 miles Bangor Cernioge horizontal mounds are level, perhaps a second level till boulders— low country also other side for mile or two— take level & look for shale — I believe sea-deposit—