The Lying Stones of Marrakech (19 page)

Again, Lavoisier's insights are subtle and detailed—and several specific predictions can be derived from his model. For example, the upper and lower
littoral beds will be confluent near the coast because the intervening pelagic bed didn't reach this far inland. Thus, a vertical section taken near the coast should show a single thick littoral bed made of large and angular pebbles. But farther away from shore, a vertical section should include a full array of alternating beds, illustrating the entire cycle and moving (top to bottom, as shown by the vertical line, located just left of center and marked 12345) from the upper littoral bed of the falling sea (1), to the intervening pelagic bed (2), to the lower littoral bed of the rising sea (3), to the underlying chalk (4), and finally to the foundation of the
ancienne terre
(5).

Thus, Lavoisier's model makes clear and specific predictions about how the sediments deposited in full cycles of rising and falling seas should be expressed in the vertical sections that had once adorned the margins of his maps with Guettard, and that represented his signal and original contribution to the developing science of geology. Moreover, the model specified predictions not only for vertical sequences in single places, but also for geographic variation in sequences from place to place. Therefore, in a last figure, Lavoisier presents some actual vertical sections measured in the field. The example presented here corresponds exacdy to his prediction for section 12345 in the idealized model. Note the perfect correspondence between Lavoisier's
“Coupe des Montagnes des environ de St. Gobain”
(section through the mountains in the neighborhood of St. Gobain) and his model (except that the actual section doesn't extend below the chalk into the ancient basement). The measured section shows four layers labeled “upper littoral,” “pelagic beds,” “lower littoral,” and “chalk” (note the layers of flint nodules in the lowermost chalk). Lavoisier had intended to write several more geological papers filled with similar empirical details to test his model. Thus, this pilot study presents only a few actual sections, but with impressive promise for continuing validation. Lavoisier had achieved a scientific innovation of the finest and most indubitable form: he had added a dimension (literally) to our knowledge of natural history.

As if he had not done enough already, Lavoisier then ended his treatise with two pages of admittedly hypothetical reasoning on the second great general theme in the study of time and history. His model of oscillating seas lies fully within the Newtonian tradition of complete and ahistorical generality. Lavoisier's oceanic cycles operate through time, but they do not express history because strings of events never occur in distinct and irreversibly directional sequences, and no single result ever denotes a uniquely definable moment. The cycles obey a timeless law of nature, and proceed in the same way no matter when they run. Cycle 100 will yield the same results as cycle 1; and the record
of rocks can never tell us where we stand in the flow of history. All variation reflects either a general environment (high or low sea) or a local circumstance (type of rock in the cliff being eroded), not the distinctive imprint of any unique and definite historical event.

Lavoisier's final plate, showing the spatial and temporal complexity of sediments deposited in a full cycle of a rising and falling sea
.

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 also invoking the fundamentally different, but intricately conjoined and equally necessary, concept of “time's arrow,” so indispensable because geology embraces history as well—and historical accounts must tell stories defined by directional sequences of unique events.

As a prerequisite for interest and meaning, history must require 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:

Lavoisier shows that an actual sequence of sediments conforms to his model of deposition in cycles of raising and lowering of sea level
.

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
“ancienne terre,”
or ancient earth. 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
I'ancienne terre…
. This is almost surely not the original earth; on the contrary, it appears that what I have called
ancienne terre
is itself composed of littoral beds much older than those depicted in the figures.

In a remarkable passage, Lavoisier then invokes what would become the classic subject for juxtaposing the yin of history (or time's arrow) against the yang of constant features built by invariant laws (time's cycle) to form a complete science of geology: the directional character of life's pageant, the primary component of the earth's rip-roaring narrative story. (By the way, Lavoisier's particular claims turn out to be wrong in every detail, but I can hardly think of an observation more irrelevant to my present point. In 1789, no one knew much about paleontological particulars. I am stressing Lavoisier's keen and correct vision that life would provide the primary source of directional history, or time's arrow.)

Lavoisier bases his claim for history upon a clever argument. He believes that rocks of the
ancienne terre
contain no fossils. But if these rocks include (as he has just argued) the same alternation of pelagic and littoral beds found in younger sediments, then the invariant physical laws of time's cycle should lead us to expect fossils in these strata—for such sediments form in environments that now teem with life. Therefore, time's arrow of directional history must explain the
difference. Physical conditions of the
ancienne terre
could not have differed from later circumstances that generated similar sediments, but the earth must then have housed no living creatures if these identical rocks contain no fossils.

Lavoisier then argues that sediments occasionally found below the Chalk (the oldest rocks with marine fossils), but above the
andenne terre
, often contain fossils of plants. He therefore envisages a threefold directional history of life: an original earth devoid of organisms, followed by the origin of vegetation on land, and finally culminating in the development of animal life both in the sea and on land:

It is very remarkable that the Chalk is usually the youngest rock to contain shells and the remains of other marine organisms. The beds of shale that we sometimes find below the Chalk often include vestiges of floating bodies, wood, and other vegetable matter thrown up along the coasts…. If we may be allowed to hazard a guess about this strange result, I believe we might be able to conclude, as Mr. Monge has proposed [the important French mathematician Gaspard Monge, who served with Lavoisier on the revolutionary commission to devise the metric system], that the earth was not always endowed with living creatures, that it was, for a long time, an inanimate desert in which nothing lived, that the existence of vegetables preceded that of most animals, or at least that the earth was covered by trees and plants before the seas were inhabited by shellfish.

And thus, hurriedly, at the very end of a paper intended only as a preliminary study, an introductory model to be filled in and fleshed out with extensive data based on field research, Lavoisier appended this little conjectural note—to show us, I suspect, that he grasped the full intellectual range of the problems set by geology, and that he recognized the power of combining a firm understanding of timeless and invariant laws -with a confident narration of the rich directional history of an ancient earth. His last page bubbles with enthusiasm for future plans involving the whole earth, a project so soon cut off by the evil that only men can do. Consider the poignant paragraph just following his speculation about the history of life:

In the next article, I will discuss in very great detail these opinions, which really belong more to Mr. Monge than to myself. But it is
indispensable that I first establish, in a solid way, the observations on which they are based.

I don't know why Lavoisier's execution affects me so deeply. We cannot assert with confidence that he would have completed his geological projects if he had lived (for all creative careers remain chock full of unrealized plans); and we know that he faced his end with a dignity and equanimity that can still provide comfort across the centuries. He wrote in a last letter:

I have had a fairly long life, above all a very happy one, and I think that I shall be remembered with some regrets and perhaps leave some reputation behind me. What more could I ask? The events in which I am involved will probably save me from the troubles of old age. I shall die in full possession of my faculties.

Lavoisier needs no rescue, either from me or from any modern author. Yet speaking personally (a happy privilege granted to essayists ever since Montaigne invented the genre for this explicit purpose more than two hundred years before Lavoisier's time), I do long for some visceral sense of fellowship with this man who stands next to Darwin in my private pantheon of intellectual heroes. He died through human cruelty, and far too young. His works, of course, will live—and he needs no more. But, and I have no idea why, we also long for what I called visceral fellowship just above—some sense of
physical continuity
, some sign of an
actual presence
to transmit across the generations, so that we will not forget the person behind the glorious ideas. (Perhaps my dedication to such material continuity only marks a personal idiosyncrasy—but not, I think, a rare feeling, and certainly concentrated among those who choose paleontology for a profession because they thrill to the objective records of life's continuous history.)

So let me end with a personal testimony. Through the incredible good fortune of an odd coincidence in good timing and unfathomable pricing, I was able to buy a remarkable item at auction a while ago—the original set of proof plates, each personally signed by Lavoisier, of the seven figures (including the three reproduced here) that accompany his sole geological article of 1789. Two men signed each plate: first, in a thick and bold hand, Gabriel de Bory, vice-secretary of the Academy of Sciences (signed “Bory Vice-Secretaire”); and second, in a much more delicate flow composed of three flourishes surrounding the letters of his last name alone, Antoine-Laurent Lavoisier.