Editing James Hutton (section)

==Theory of rock formations==
Hutton developed several hypotheses to explain the [[rock formations]] he saw around him, but according to Playfair he "was in no haste to publish his theory; for he was one of those who are much more delighted with the contemplation of truth, than with the praise of having discovered it". After some 25 years of work,<ref name=geo3>{{cite web |url=http://www.james-hutton.org.uk/One/Geology/03.htm |archive-url=https://archive.today/20120908090215/http://www.james-hutton.org.uk/One/Geology/03.htm |url-status=dead |archive-date=8 September 2012 |title=Theory of the Earth |access-date=11 April 2008 |publisher=James Hutton.org.uk }}</ref> his ''[[Theory of the Earth]]; or an Investigation of the Laws observable in the Composition, Dissolution, and Restoration of Land upon the Globe'' was read to meetings of the [[Royal Society of Edinburgh]] in two parts, the first by his friend [[Joseph Black]] on 7 March 1785, and the second by himself on 4 April 1785. Hutton subsequently read an abstract of his dissertation ''Concerning the System of the Earth, its Duration and Stability'' to Society meeting on 4 July 1785,<ref name=TOE/> which he had printed and circulated privately.<ref name=abstract/> In it, he outlined his theory as follows;

{{blockquote|The solid parts of the present land appear in general, to have been composed of the productions of the sea, and of other materials similar to those now found upon the shores. Hence we find reason to conclude:<br />
1st, That the land on which we rest is not simple and original, but that it is a composition, and had been formed by the operation of second causes.<br />
2nd, That before the present land was made, there had subsisted a world composed of sea and land, in which were tides and currents, with such operations at the bottom of the sea as now take place. And,

Lastly, That while the present land was forming at the bottom of the ocean, the former land maintained plants and animals; at least the sea was then inhabited by animals, in a similar manner as it is at present.<br />
Hence we are led to conclude, that the greater part of our land, if not the whole had been produced by operations natural to this globe; but that in order to make this land a permanent body, resisting the operations of the waters, two things had been required;<br />
1st, The consolidation of masses formed by collections of loose or incoherent materials;<br />
2ndly, The elevation of those consolidated masses from the bottom of the sea, the place where they were collected, to the stations in which they now remain above the level of the ocean.}}

===Search for evidence===
[[File:Hutton's Glen Tilt exposure at Dail-an-eas Bridge.jpg|thumb|upright|Hutton's [[Glen Tilt]] exposure at collapsed Dail-an-eas Bridge upstream from Forest Lodge, drawn by John Clerk of Eldin in 1785. The bridge collapsed in approximately 1973.   Location: {{Coord| 56.851082| -3.741822|display=inline|name=Dail-an-eas bridge}}]]
[[File:Dike in Tay near Stobhall.jpg|thumb|Intrusive dike eroded by the [[River Tay]] near Stobhall described by Hutton.    Location: {{Coord| 56.48964| -3.42455|display=inline|name=dike near Stobhall}}]]
[[File:Dike_in_Garry_at_Dalnacardoch.jpg|thumb|Geological dike eroded by the [[River Garry, Perthshire|River Garry]] at Dalnacardoch described by Hutton and drawn by Clerk.    Location: {{Coord| 56.880493| -4.09473|display=inline|name=Dalnacardoch dikes}}]]
[[File:Hutton's Section, Salisbury Crags.jpg|thumb|right|Hutton's Section on Edinburgh's [[Salisbury Crags]].  Location: {{Coord| 55.9432| -3.1672|display=inline|name=Hutton's Section at Salisbury Crags}}]]
In the summer of 1785 at [[Glen Tilt]] and other sites in the [[Cairngorms|Cairngorm mountains]] in the [[Scottish Highlands]], Hutton found [[granite]] penetrating [[metamorphic rock|metamorphic]] [[schist]]s, in a way which indicated that the granite had been [[molten]] at the time. This was Hutton's first geological field trip and he was invited by the Duke of Atholl to his hunting lodge, Forest Lodge. The exposures at the Dail-an-eas Bridge demonstrated to him that granite formed from the cooling of molten rock rather than it [[Precipitation (chemistry)|precipitating]] out of water as others at the time believed, and therefore the granite must be younger than the schists.<ref name="Macfarlane">{{cite news |url=http://www.accessmylibrary.com/article-1G1-109847321/glimpses-into-abyss-time.html |title=Glimpses into the abyss of time |author=Robert Macfarlane |publisher=[[The Spectator]] |date=13 September 2003 |quote=Hutton possessed an instinctive ability to reverse physical processes – to read landscapes backwards, as it were.  Fingering the white quartz which seamed the grey granite boulders in a Scottish glen, for instance, he understood the confrontation that had once occurred between the two types of rock, and he perceived how, under fantastic pressure, the molten quartz had forced its way into the weaknesses in the mother granite. }}</ref><ref name=tilt>{{cite web |url=http://www.scottishgeology.com/geo/regional-geology/grampian/glen-tilt/ |title=Glen Tilt |publisher=Scottish Geology |access-date=3 May 2011 |archive-date=6 May 2020 |archive-url=https://web.archive.org/web/20200506211517/https://www.scottishgeology.com/geo/regional-geology/grampian/glen-tilt/ |url-status=dead }}</ref> Hutton presented his theory of the earth on 4 March and 7 April 1785, at the Royal Society of Edinburgh.<ref>Stephen J. Gould, page 70, Time's Arrow, Time's Circle, 1987</ref>

He went on to find a similar penetration of [[volcanic rock]] through [[sedimentary rock]] in [[Edinburgh]], at [[Salisbury Crags]],<ref name="Denby"/> adjoining [[Arthur's Seat]] – this area of the Crags is now known as Hutton's Section.<ref>[https://archive.today/20061023161737/http://www.scottishgeology.com/outandabout/classic_sites/locations/huttons_section.html Scottish Geology – Hutton's Section at Salisbury Crags]<br />[http://www.scottishgeology.com/geo/regional-geology/midland-valley/salisbury-crags-edinburgh/ Scottish Geology – Hutton's Rock at Salisbury Crags] {{Webarchive|url=https://web.archive.org/web/20180809112754/http://www.scottishgeology.com/geo/regional-geology/midland-valley/salisbury-crags-edinburgh/ |date=9 August 2018 }}</ref><ref>{{cite web |author=Cliff Ford |url=http://www.geos.ed.ac.uk/undergraduate/field/holyrood/huttonsloc.html |title=Hutton's Section at Hoyrood Park |publisher=Geos.ed.ac.uk |date=1 September 2003 |access-date=3 May 2011 |archive-date=24 June 2011 |archive-url=https://web.archive.org/web/20110624115935/http://www.geos.ed.ac.uk/undergraduate/field/holyrood/huttonsloc.html |url-status=dead }}</ref> He found other examples in [[Galloway]] in 1786, and on the [[Isle of Arran]] in 1787.

[[File:Hutton's Unconformity - geograph.org.uk - 68546.jpg|thumb|right|Hutton's Unconformity on Arran]]
[[Image:Hutton Unconformity , Jedburgh.jpg|thumb|right|Hutton Unconformity at [[Jedburgh]].  Photograph (2003) below [[John Clerk of Eldin|Clerk of Eldin]] illustration (1787).   Location: {{Coord| 55.4721| -2.5545|display=inline|name=Hutton Unconformity , Jedburgh}}]]
The existence of [[unconformity|angular unconformities]] had been noted by [[Nicolas Steno]] and by French geologists including [[Horace-Bénédict de Saussure]], who interpreted them in terms of [[Neptunism]] as "primary formations". Hutton wanted to examine such formations himself to see  "particular marks" of the relationship between the rock layers. On the 1787 trip to the [[Isle of Arran]] he found his first example of [[Hutton's Unconformity]] to the north of Newton Point near [[Lochranza]],<ref name=arnmuseum>{{cite web|url=http://www.arranmuseum.co.uk/what-will-you-see/geology/virtual-field-trips/|title=Hutton's Unconformity |date=2014 |publisher=[[Isle of Arran]] Heritage Museum |access-date=20 November 2017 }}</ref><ref name=Waymarking>{{cite web |url=http://www.waymarking.com/waymarks/WM3F65 |title=Hutton's Unconformity – Lochranza, Isle of Arran, UK – Places of Geologic Significance on Waymarking.com |access-date=20 October 2008}}</ref> but the limited view meant that the condition of the underlying strata was not clear enough for him,<ref name=monty>{{cite web |url=http://nagt.org/files/nagt/jge/abstracts/Montgomery_v51n5.pdf |title=Siccar Point and Teaching the History of Geology |access-date=26 March 2008 |author=Keith Montgomery |year=2003 |publisher=University of Wisconsin }}</ref> and he incorrectly thought that the strata were conformable at a depth below the exposed outcrop.<ref name=Rance>{{cite web |url=http://geowords.com/histbookpdf/a22.pdf |title=Hutton's unconformities |author=Hugh Rance |year=1999 |work=Historical Geology: The Present is the Key to the Past |publisher=QCC Press |access-date=20 October 2008 |archive-url=https://web.archive.org/web/20081203173042/http://www.geowords.com/histbookpdf/a22.pdf |archive-date=3 December 2008 |url-status=dead  }}</ref>

Later in 1787 Hutton noted what is now known as the Hutton or "Great" Unconformity at Inchbonny,<ref name="VestigeProspectAMNH"/> [[Jedburgh]], in layers of [[sedimentary rock]].<ref name="Unconformity Jedburgh">{{cite web |url=http://www.jedburgh-online.org.uk/aroundjedburgh.asp |title=Jedburgh: Hutton's Unconformity |work=Jedburgh online |quote=Whilst visiting Allar's Mill on the Jed Water, Hutton was delighted to see horizontal bands of red sandstone lying 'unconformably' on top of near vertical and folded bands of rock. |url-status=dead |archive-url=https://web.archive.org/web/20100809184047/http://www.jedburgh-online.org.uk/aroundjedburgh.asp |archive-date=9 August 2010  }}</ref> As shown in the illustrations to the right, layers of [[greywacke]] in the lower layers of the cliff face are tilted almost vertically, and above an intervening layer of [[Conglomerate (geology)|conglomerate]] lie horizontal layers of [[Old Red Sandstone]]. He later wrote of how he "rejoiced at my good fortune in stumbling upon an object so interesting in the natural history of the earth, and which I had been long looking for in vain." That year, he found the same sequence in [[Teviotdale]].<ref name=monty/>

[[Image:Siccar Point red capstone closeup.jpg|thumb|right|An eroded outcrop at [[Siccar Point]] showing sloping red sandstone above vertical greywacke was sketched by Sir James Hall in 1788.  Location: {{Coord| 55.9315| -2.3013|display=inline|name=Hutton Unconformity , Jedburgh}}]]
In the Spring of 1788 he set off with [[John Playfair]] to the [[Berwickshire]] coast and found more examples of this sequence in the valleys of the Tour and Pease Burns near [[Cockburnspath]].<ref name=monty/> They then took a boat trip from Dunglass Burn east along the coast with the geologist [[Sir James Hall, 4th Baronet|Sir James Hall]] of [[Dunglass]]. They found the sequence in the cliff below St. Helens, then just to the east at [[Siccar Point]] found what Hutton called "a beautiful picture of this junction washed bare by the sea".<ref>{{cite web |url=http://www.james-hutton.org.uk/One/Geology/05.htm |archive-url=https://archive.today/20120802194541/http://www.james-hutton.org.uk/One/Geology/05.htm |url-status=dead |archive-date=2 August 2012 |title=Hutton's Journeys to Prove his Theory |publisher=James-hutton.org.uk |access-date=3 May 2011 }}</ref><ref>{{cite web |url=http://www.snh.org.uk/publications/on-line/geology/elothian_borders/hutton.asp |title=Hutton's Unconformity |publisher=Snh.org.uk |access-date=3 May 2011 |archive-url=https://web.archive.org/web/20150924104617/http://www.snh.org.uk/publications/on-line/geology/elothian_borders/hutton.asp |archive-date=24 September 2015 |url-status=dead  }}</ref> Playfair later commented about the experience, "the mind seemed to grow giddy by looking so far into the abyss of time".<ref name="Playfair RSE">{{cite news|url=http://findarticles.com/p/articles/mi_m1134/is_5_108/ai_54830705 |archive-url=https://archive.today/20120708195026/http://findarticles.com/p/articles/mi_m1134/is_5_108/ai_54830705 |url-status=dead |archive-date=8 July 2012 |title=Hutton's Unconformity |author=John Playfair |work=Transactions of the [[Royal Society of Edinburgh]], vol. V, pt. III, 1805, quoted in [[Natural History (magazine)|Natural History]], June 1999 |year=1999 |author-link=John Playfair }}</ref> Continuing along the coast, they made more discoveries including sections of the vertical beds showing strong ripple marks which gave Hutton "great satisfaction" as a confirmation of his supposition that these beds had been laid horizontally in water. He also found conglomerate at altitudes that demonstrated the extent of erosion of the strata, and said of this that "we never should have dreamed of meeting with what we now perceived".<ref name=monty/>

Hutton reasoned that there must have been innumerable cycles, each involving [[Deposition (sediment)|deposition]] on the [[seabed]], uplift with tilting and [[erosion]] then undersea again for further layers to be deposited. On the belief that this was due to the same geological forces operating in the past as the very slow geological forces seen operating at the present day, the thicknesses of exposed rock layers implied to him enormous stretches of time.<ref name="VestigeProspectAMNH"/>