Capturing the Center

Lavoisier, in other words, had worked brilliantly with the necessary concept of time's cycle, so vital for any scientific account of the past because we need general laws to explain repeated physical events. But geology cannot render a full account of the earth's past without the fundamentally different, but intricately conjoined and equally necessary, concept of time's arrow, so vital because geology also em braces history, and history requires a directional sequence of unique events--in other words, the last five letters of its own name, a story.

As a prerequisite for interest and meaning, history must unfold in a matrix of extensive time--which Lavoisier had already provided by combining his oscillating model of the oceans with empirical evidence for multiple cycles in vertical sections. If each cycle required considerable time (particularly for the formation of pelagic beds, so slowly built from the debris of organisms), then the evidence for numerous cycles implied an earth of great antiquity. By 1789 (and contrary to popular legend), few scientists still accepted a biblical chronology of just a few thousand years for the earth's history. But the true immensity of geological time still posed conceptual difficulties for many investigators, and Lavoisier's forthright claims mirrored the far more famous lines published just a year before, in 1788, by the traditional "father" of modern geology, the Scotsman James Hutton: "Time is, to nature, endless and as nothing." Lavoisier expressed his version of deep time in the more particular light of his model:

   The details that I have just discussed have no other object than to prove
   this proposition: if we suppose that the sea undergoes a very slow
   oscillatory movement, a kind of flux and reflux, that these movements occur
   during a period of several hundreds of thousands of years, and that these
   movements have already occurred a certain number of times, then if we make
   a vertical section of rocks deposited between the sea and the high
   mountains, this section must present an alternation of littoral and pelagic
   beds.

Within such a matrix of deep time, the concept of a truly scientific history obtains new meaning and promise. At the end of his treatise, Lavoisier therefore touches upon this subject in his characteristically empirical way: by returning to the lowermost layer beneath the recorded sediments of his models and measured sections--a complex of rocks that he had bypassed with the simple label l'ancienne terre. Lavoisier now states that he does not regard this foundation as part of the original earth at its time of formation, but rather as a probable series of sediments, much older than the Chalk but also built as a sequence of littoral and pelagic beds (although now hard to identify because age has obliterated the characteristic features of such deposits):

   One will no doubt want to know about the rocks found underneath the Chalk
   and what I mean by the expression l'ancienne terre.... This is almost
   surely not the original earth; on the contrary, it appears that what I have
   called l'ancienne terre is itself composed of littoral beds much older than
   those depicted in the figures.