Darwin-L Message Log 7:10 (March 1994)

Academic Discussion on the History and Theory of the Historical Sciences

This is one message from the Archives of Darwin-L (1993–1997), a professional discussion group on the history and theory of the historical sciences.

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<7:10>From jacobsk@ERE.UMontreal.CA  Mon Mar  7 19:39:43 1994

From: jacobsk@ERE.UMontreal.CA (Jacobs Kenneth)
Subject: Re: Superposition (geological)
To: darwin-l@ukanaix.cc.ukans.edu
Date: Mon, 7 Mar 1994 20:36:46 -0500 (EST)

> John Sutton asked an interesting question about the concept of
> "superposition" which he says is a hot topic now in connectionism and related
> fields.  The most common sense of the term in the historical sciences is of
> course the geological one: the "principle of superposition" says that in a
> series of geological strata, the oldest layers are on the bottom and the
> youngest layers are on the top, because sediments are deposited horizontally,
> one on top of another.  This is a very important principle of historical
> reconstruction which goes back to Steno in the 1600s at least; perhaps some
> of our historians of geology could provide more information about its
> history.

As Bob O'Hara implied here on 5 March, Steno was not the first.  As with so
many of the things Steno "discovered" (or so I am told by one of my students,
who provided the following info), Avicenna said it first (in the early 11th
century) and often in the very same manner in which it was later said.  Here
is part of Avicenna's discussion of mountain formation:

"It is possible that each time the land was exposed by the ebbing of
the sea a layer was left, since we see that some mountains appear to
have been piled up layer by layer, and it is therefore likely that the
clay from which they were formed was itself at one time arranged in
layers.  One layer was formed first, then, at a different period, a
further layer was formed and piled [upon the first, and so on]."

        p.31, in "Section on stones and minerals" in _Avicennae,
De congelatione et conglutinatione lapidum_.  ("Being sections of the
'Kitab Al-Shifa.'  The Latin and Arabic texts edited with an English
translation of the latter and with critical notes)  E.J. Holmyard & D.C.
Mandeville (eds.)  Paris: Librairie Orientaliste Paul Geunther, 1927.

	There are other passages with similar conclusions.  Interestingly,
no mention is ever made of the implication that the lower strata are _older_,
the antiquity of the layers (and the things found in them) being wholly un-
interesting.  There are a bunch of reasons for this, but I'll have to wait
until the student's thesis is done to recount them.

Ken Jacobs
Universite de Montreal

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