RECORD: Darwin, C. R. Geological diary: Hypothesis / S Cruz. [4-5.1834] CUL-DAR34.115-117 Transcribed by Kees Rookmaaker, edited by John van Wyhe (Darwin Online,

REVISION HISTORY: Transcribed by Kees Rookmaaker, corrections and editing by John van Wyhe 3.2011. RN1

NOTE: This document, part of the largest scientific document composed by Darwin during the voyage of the Beagle, is written mostly in ink. Marginal notes are here integrated into the text.

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Reproduced with the permission of the Syndics of Cambridge University Library and William Huxley Darwin.

See the introduction to the Geological Diary by Gordon Chancellor.


S. Cruz. —


From a break in the mountains (examples & ask), the sea was deeper on the East coast from the stream: after some elevations, this space formed a lagoon, bounded on all sides by the highest inland cliffs & alluvium; it cut a channel & had a horizontal bed. — Another (or many raised) this space to such an extent, so that we will say the water bottom was 200 feet deep. & its beds 450 feet at

The bottom of the sea is now 450 above sea. supposing that the water was a certain period shallow from upheavals & silting we will call it 4 300 feet: — let us then consider, what took place was the case when its waters were on a level with the sea. that the land is 75 below its present altitude. — The coast 840 cliffs. would be just showing & along whole sides the valley. & from inclination in bottom assumed (350) these same ones near to the sea coas Andes. would be so many feet above. (& cut into steps if there had been many elevations) ∴ a or nearly horizontal bed would now wate formed. which perhaps is the 2d plain: the parts however most to the East would be formed rather subsequently to the West. without the elevations were large ones) — Let another elevation of 200 feet take place: the 350 plain would just be

115 verso [blank]



nearly apparent at the coast, but 250 350 above the channel every where else. — at this period some of the 3d plains were formed: Another elevation & the sea would be dry: but yet channels are generally very deep. hence a deposit would be formed: which would make another plain. (again repeat this); these 4 & 5th plains are only seen a good way to the East, where the sea would be deeper, more like an estuary. — More elevation the river would be formed & flow out its present channel: 350 cliffs would assume their present elevation & the bed of lake would be elevated to its present position

116 verso

If the force of upheaval acted in line parallel to earths form the plain at any point ought to be 350 + 200 the presumed depth at that the [external] point:

if we suppose in the distance between S. Cruz & (Z) plain on the 28th there was an increase in depth of 80 fathom. — the distance being 90 miles, we ought to find the plan plain which at the coast is 350 to be here + 480 = 830. — Now Z plain is 525 above river & river above sea 360 = 885 feet which agreement (difference only 50 ft) is quite near enough.

I am afraid 80 fathoms is too much to assume.

I see on same principle on the 30th (perhaps 15 miles to the west we must have a shoaling of 16 fathoms or 102 feet & rise of river: —

But (Z) plain is the last in which any confidence can be placed

Work the Falkland inclination. Find P

[sketch] Z base P to sea

(Z) plain is jammed up amongst lava


correct heights & [illeg] these observations of plains

The rise of cliffs going up valley [sketch]



In the 28th — Perhaps judging from the Falkland soundings, 270 would be the part raised. — may be separated by fall of river. —

That is parts spots of equal at [ink smudge] above the river & on coast were same layer & at same time raised: — We have conjectured the lo inland cliffs to be 950 feet high (good reason) = exactly Port St Julian & probably St Cruz

for you cannot expect in a coast sounding to agree at equal distance to within 20 fathom: —

The alluvial hill is an extra deposit on the gravel & on the lava

[sketch] lava

The Sts would not be more than 100 miles long

arguments for Sts modern shells

Theory applicable to many rivers

Main rivers Negro & Colorado same [illeg]

117 verso



                1168] or 950?          
                      1426 1122 [1416  
840                     212 edge of lava  
                958] or 740     910 thickness of
+ gravel 637
                Crater hill          
14 355 418   419 383 429 575 525     587   310
  Gravel Gravel ?   Higer lava? main lava plain 65 + gravel (Z)     oyster bed   old alluv:
= 35 thick? 52. thick ?   for lava cliff 117. thick, vase     plain lava ?        
      185? 278 262. above river 414              
3d. plain conjectured thickness
78 ft??
  lava plain     conjectured        
A B   C D E   H     K      
S.Cruz   Noon cliff                      
    28th 26th 26th 27     28th 29th 30th
May 1st

(B) might be expected to be higher than A because nearer than 6 miles to highest inland? —

(C) Higher lava is probably from inclination of stream a little lower than (381) plain. —

(D). ؟ whether thickness is not greater for more to the West East we have top of cliff only 278. — now assuming thickness only 30 feet will make lower limit 248, the other base being 262. — In so short a distance, the bottom would not have such an inclination more than inclination of the river ?? —

(E) Substance on lava being too (in proportion) high. has subjected it to much denudation at B I daresay inland cliffs. were about same height as (840)

[calculation] 98 [+] 65 [=] 163

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