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The sharp-eyed lynx, outfoxed by nature. (Part 2) (observations of fossil wood by Francesco Stelluti)
Author/s: Stephen Jay Gould
In the city of Rome, in 1603, several natural philosophers founded modern Europe's first scientific society. They called themselves the Lynxes, choosing this animal as their symbol because it was believed to be endowed with superlative sharpness of vision. In Part One of this essay, the author showed how the preeminent Lynx, astronomer Galileo Galilei, published flawed "observations" about Saturn. Part Two argues that Galileo's fellow Lynx Francesco Stelluti fell into a similar trap.
Part Two: Francesco Stelluti and the Mineral Wood of Aquasparta
Francesco Stelluti remained faithful to Galileo during the great physicist's last years of internal exile and arrest. On November 3, 1635, he wrote a long and interesting letter to Galileo at Arcetri, trying to cheer his friend with news from the world of science. Stelluti first expressed his sympathy for Galileo's plight: "God knows how grieved and pained I am by your ordeal" (Dio sa quanto mi son doluto e doglio de' suoi travagli). Stelluti then attempted to raise Galileo's spirits with the latest report on an old project of the Lynxesan analysis of some curious fossil wood found on the estate of their leader, Federico Cesi, the duke of Aquasparta:
You should know that while I was in
Rome, Signor Cioli visited the duchess
[Cesi's widow] several times and that she
gave him, at his departure, several
pieces of the fossil wood that is born near
Aquasparta. He wanted to know where it
was found and how it was generated....
for he noted that Prince Cesi, of blessed
memory, had planned to write about it.
The duchess then asked me to write something
about this, and I have done so and
sent it to Signor Cioli, together with a
package of several pieces of the wood,
some petrified and some just beginning to
This fossil wood had long vexed and fascinated the Lynxes. Stelluti had described the problem to Galileo in a letter of August 23, 1624, written just before the Lynxes' convention and the fateful series of events initiated by Stelluti's microscopical drawings of bees, intended to curry favor with the new pope (and described in Part I of my essay).
Our lord prince [Cesi] kisses your hands
and is eager to hear good news from
you. He is doing very well, despite the
enervating heat, which does not cause
him to lose any time in his studies and
most beautiful observations on this
mineralized wood. He has discovered several
very large pieces, up to eleven
palms [of the human hand, not the tree
of the same name] in diameter, and others
filled with lines of iron, or a material
similar to iron. . . . If
you can stop by here on your return to
Florence, you can see all this wood and
where it is born and some of the nearby
mouths of fire [steaming volcanic pits
near Aquasparta that played a major role in
Stelluti's interpretation of the wood].
You will observe all this with both surprise and
We don't usually think of Galileo as a geologist or paleontologist, but his catholic interests (with a small c!) encompassed everything that we would now call science, including all of natural history. Galileo did take his new telescope to his first meeting, in 1611, with Cesi and the Lynxes, and all members became enthralled with Galileo's reconstructed cosmos. But he also brought to the same meeting a curious stone recently discovered by some alchemists in Bologna and called the lapis bononiensis (Bologna stone) or the "solar sponge," for the rock seemed to absorb and then reflect the sun's light. The specimens have been lost, and we still don't know the composition or the nature (found in the earth or artificially made) of Galileo's stone (some scholars conjecture that it may have been barium sulfide). But we do know that the Lynxes were entranced. Cesi, committed to a long stay at his estate in Aquasparta, begged Galileo for some specimens, which arrived in the spring of 1613. Cesi then wrote to Galileo: "I thank you in every way, for truly this is most precious, and soon I will enjoy the spectacle that, until now, absence from Rome has not permitted me." (I read this quotation and information about the Bologna stone in Paula Findlen's excellent book Processing Nature University of California Press, 1994].)
Galileo then took a reciprocal interest in Cesis geological discovery--the fossil wood of Aquasparta--so Stelluti's letters reflect a clearly shared interest. Cesi did not live to publish his controversial theories on this fossil wood. Therefore, the ever loyal Stelluti gathered the material together, wrote his own supporting text, engraved thirteen lovely plates, and published his most influential work (with the possible exception of those earlier bees) in 1637 under a title almost as long as the text of the treatise: Trattato del legno fossile minerale nuovamente scoperto, nel quale brevemente si accenna la varia & mutabil natura di detto Legno, rappresentatovi con alcune figure, che mostrano il luogo dove nasce, la diversita dell'onde, che in esso si vedono, e le sue cosi varie, e maravigliose forme (Treatise on newly discovered fossil mineralized wood, in which we point out the diverse and mutable nature of this wood, as represented by several figures, which show the place where it is born, the diversity of waves [growth lines] that we see in it, and its highly varied and marvelous forms).
The title page illustrates several links with Galileo's 1613 Letters on Sunspots. Note the similar design and the same publisher (Mascardi in Rome) for the two works. Both feature the official emblem of the Lynxes--the standard picture of the animal (copied from Konrad Gesner's 1551 compendium) surrounded by a laurel wreath and topped by the crown of Cesi's noble family. Both authors announce their affiliation by their name--the volume on sunspots by Galileo Galilei Linceo, the treatise on fossil wood by Francesco Stelluti Accad. Linceo. The ghosts of Galileo's tragedy also haunt Stelluti's title page, which bears a date of 1637 (lower right in Roman numerals), when Galileo lived in confinement at Arcetri secretly writing his own last book, which would be published the following year. Moreover, Stelluti dedicates his treatise quite obsequiously "to the most eminent and most revered Signor Cardinal Francesco Barberini" (in letters larger than the type used for Stelluti's own name), the nephew of the pope who had condemned Galileo, and the man who had refused Stelluti's invitation to lead (and save) the Lynxes after Cesis death.
But the greatest and deepest similarity between Galileo's book on sunspots and Stelluti's treatise on fossil wood far transcends any visual likenesses and resides instead in the nature of a conclusion and a basic style of rhetoric and scientific procedure. (This similarity struck me forcefully when I bought a copy of Stelluti's treatise last month, read the text, remembered the old tale of Galileo and Saturn, and then formulated the theme for this essay. As I pursued my research, I then became stunned by the eerie and uncanny series of more specific links that I discovered between Stelluti and Galileo, including the likenesses in the two tide pages.) Galileo presented his major discussion of Saturn in this 1613 book on sunspots (as quoted in Part I of this essay), where he advocated an entirely false interpretation that he regarded as necessarily correct because he had observed the phenomenon with his own eyes. Stelluti's treatise on fossil wood presents a completely false (actually backward) interpretation of Cesis discovery and then uses exactly the same tactic of arguing for the necessary truth of this view--because he had personally observed the phenomena he described.
Despite some practical inconveniences imposed by ruling powers committed neither to democracy nor pluralism (one might, after all, end up burned at the stake like Giordano Bruno, or merely arrested, tried, convicted, and restricted like Galileo), the first half of the seventeenth century must rank as an apogee of excitement for scientists. The most fundamental questions about the structure, meaning, and causes of natural phenomena all opened up anew, with no clear answers apparent and the most radically different alternatives plausibly advocated by major intellects. By inventing a simple device for closer viewing of the heavens, Galileo fractured the old conception of nature's grandest scale. Meanwhile, on earth, other scientists raised equally deep an disturbing questions about the very nature of matter and the basic modes of change and causality.
The nascent science of paleontology played a major role in this reconstruction of reality--primarily by providing crucial data to resolve the two debates that convulsed (and virtually defined) the profession in Stelluti and Galileo's time:
(1) What do fossils represent? Are they invariably the remains of organisms that lived in former times and became entombed in rocks, or can they be generated inorganically as products of formative forces within the mineral kingdom? (If such regular forms as crystals and such complex shapes as stalactites can arise inorganically, why should we deny that other petrified bodie's strongly resembling animals and plants might be products of the mineral kingdom as well?)
(2) How shall we arrange and classify natural objects? Is nature built as a single continuum of complexity and vitality, a chain of being rising without a gap from dead and formless muds and clays to the pinnacle of humanity, perhaps even to God himself? Or can natural objects be placed into sharply separated and immutably established realms, each defined by such different principles of structure that no transitional forms between realms could even be contemplated? Or, in more concrete terms, does the old tripartite division of mineral, vegetable, and animal represent three loosely defined domains within a single continuum (with transitional forms between minerals and vegetables and between vegetables and animals) or a set of three utterly disparate modes, each serving as a distinct principle of organization for a unique category of natural objects?
Cesi had always argued, with force and eloquence, that the study of small objects on earth could yield as much reform and insight for science as Galileo's survey of the heavens. The microscope, in other words, would be as valuable as the telescope. Cesi wrote:
If we do not know, collect, and master the
smallest things, how will we ever succeed in
grasping the large things, not to mention
the biggest of all? We must invest our
greatest zeal and diligence in the treatment
and observation of the smallest objects.
The largest of fires begins with a small spark;
rivers are born from the tiniest drops, and
grains of sand can build a great hill.
Therefore, when Cesi found a puzzling deposit of petrified wood near his estate, he used these small and humble fossils to address the two great questions outlined above--and he devised the wrong answer for each. Cesi argued that his fossil wood had arisen by transformation of earths and clays into forms resembling plants. His "wood" had therefore been generated from the mineral kingdom, proving that fossils could form inorganically. Cesi then claimed that his fossils stood midway between the mineral and vegetable kingdoms, providing a smooth bridge along a pure continuum. Nature must therefore be constructed as a chain of being. (Cesi had been committed to this position for a long time, so he can scarcely be regarded as a dispassionate or disinterested observer of fossils. His botanical classification, eventually published by Stelluti in 1651, arranged plants in a rising series from forms that he regarded as most like minerals to species that he viewed as most like animals.) Since Cesi could not classify his fossils into any conventional kingdom, he awarded them a separate name for a novel realm between minerals and plants--the metallophytes.
Stelluti, playing his usual game of follow-the-leader, devoted his 1637 treatise to supporting Cesi's arguments for the transitional status of metallophytes and their origin in the mineral kingdom from transmuted earths and clays. The fossils may look like plants, but they are "born" (in Stelluti's phrase) from the heated earths of the surrounding countryside (where subterranean magmas boll the local waters, thus abetting the conversion of loose earth to solid metallophyte). Stelluti concludes:
The generation of this wood proceeds not
from the seed or root of any plant but from
a kind of earth, very much like clay, which
little by little becomes transmuted to wood.
Nature operates in such a manner until all
this earth is converted into that kind of
wood. And I believe that this occurs with
the aid of heat from subterranean fires,
which are found in this region.
To support this conclusion, Stelluti presented the following five basic arguments:
(1) The fossil wood, generated from earth, reproduces only the forms of tree trunks, never any other parts of true plants:
It is clear that this wood is not born from
seeds, roots, or branches, like other plants,
because we never find pieces of this wood
with roots or branches or nerves [internal
channels for fluids] as in other [truly
vegetable] wood and trees, but only simple
trunks of varied form.
(2) The fossil trunks are not rounded, as in true trees, but rather compressed to oval shapes, because they must grow in situ from earths flattened by the weight of overlying sediments (see the accompanying reproduction of Stelluti's figures):
I believe that they adopt this oval shape
because they must form under a great mass
of earth, and cannot grow against the
overlying weight to achieve the circular, or
rather cylindrical, form assumed by the
trunks of true trees. Thus, I can securely
affirm that the original material of this
wood must have been earth of a clayey
(3) Five of Stelluti's plates present detailed drawings (perhaps done, in part, with the aid of a microscope) of growth lines in the fossil wood. Stelluti's argument for these inner details of structure follow his claim (just above) for the outward form of entire specimens: the growth lines form wandering patterns reflecting irregular pathways of generation from earth, following limits imposed by the weight of overlying sediments. They never form in regular concentric circles, as in true trees. Stelluti therefore calls them onde, or "waves," rather than growth lines:
The waves and veins are not continuous,
all following the same form, as in
[vegetable] wood, but are shaped in a
variety of ways--some long and straight,
others constricted, others thick, others
contorted, others meandering. . . . This
mineral wood takes its shape from the press
of the surrounding earth, and thus it has
waves of such varied form.
(4) In the argument that he regarded as most decisive, Stelluti holds that many specimens have been found in the process of transition, with some parts still made of shapeless earth, others petrified in the shapes and forms of wood, and still others fully converted to wood. Stelluti views these stages as an actual sequence of transformation. He writes about a large specimen, exposed in situ:
In a ditch, we discovered a long layer of this
wood . . . rather barrel-shaped, with one
segment made of pure earth, another of
mixed earth and wood, and another of pure
wood. . . . We may therefore call it earth
wood [creta legno].
Later, he draws a smaller specimen (also reproduced here from Stelluti's figures) and states:
The interior part is made of wood and
metal together, but the crust on the outside
seems to be made of lateritic substance--that
is, of terra-cotta, as we find in bricks.
(5) In a closing (and conclusive) flourish for the empirical method, Stelluti reports the results of a supposed experiment done several years before:
A piece of damp earth was taken form the
interior of a specimen of this wood and
placed in a room of the palace of
Aquasparta, belonging to Duke Cesi. After
several months, it was found to be completely
converted into wood--as seen, not without
astonishment, by the aforementioned Lord,
and by others who viewed it. And not a
single person doubted that earth is seed and
mother of this wood [la terra e seme e
madre di questo legno].
With twentieth-century hindsight, we can easily see how Stelluti fell into error and told his story backward. His specimens are ordinary fossil wood, the remains of ancient plants. The actual sequence of transformation runs from real wood, to replacement of wood by minerals (petrifaction), to earth that may either represent weathered and degraded petrified wood or may just be deposited on or inside the wood by percolating waters. In other words, Stelluti ran the sequence backward, in his crucial fourth argument, from formless earth to metallophytes located somewhere between the mineral and vegetable kingdoms.
Moreover, Stelluti's criteria of shaping by overlying sediments (arguments 2 and 3) work just as well for original wood later distorted and compressed as for his reverse sequence of metallophytes actively growing within restricted spaces. Delicate parts fossilize only rarely, so the absence of leaves and stems and the restriction of specimens to trunks only record the usual pathways of preservation for ancient plants, not Stelluti's naive idea (argument 1) that the tree trunks cannot belong to the kingdom of vegetables unless fossilized seeds or roots can also be found. As for the supposedly crucial experiment (argument 5)--well, what can we do with an undocumented 300-year-old verbal report that ranked only as hearsay even for Stelluti himself?
Nonetheless, Stelluti's treatise played an important role on the wrong side of the great debate about the nature of fossils--a major issue throughout seventeenth-century science and not fully resolved until the mid-eighteenth century (see "The Lying Stones of Wurzburg and Marrakech," April 1998, for a late defense, from 1726, of Stelluti's general view). Important authors throughout Europe, from Robert Plot in England (1677) to Olaus Worm in Denmark (1655), reported Stelluti's work to support the view that fossils arise within the mineral kingdom and are not the remains of organisms. (Stelluti, by the way, did not confine his arguments to the wood of Aquasparta, but made a general extrapolation to the nature and status of all fossils. In a closing argument, depicted on a fateful thirteenth plate of ammonites, Stelluti held that all fossils belong to the mineral kingdom and grow within rocks.)
When we evaluate the logic and rhetoric of Stelluti's arguments, one consistent strategy stands out above all else. Stelluti had finally become a true disciple of Galileo and of the primacy of direct empirical observation, viewed as inherently objective. Over and over again, Stelluti states that we must accept his conclusions because he has seen the phenomenon, often several times over many years, with his own eyes.
Stelluti had used this Galilean rhetoric to great advantage before. At the bottom of his beautiful 1625 engraving of three bees for Pope Urban VIII (Maffeo Barberini), Stelluti had added a little Latin note just under his greatest enlargement of paired bee legs. In a phrase almost identical in form to Galileo's anagram about Saturn, Stelluti wrote: Franciscus Stellutus Lynceus [Fabr.sup.is] Microscopio Observavit (The Lynx Francesco Stelluti from [the town of] Fabriano observed [these objects] with a microscope). This time, and for once, Stelluti had a leg up on Galileo--for the "slow stepper" among the Lynxes had made accurate observations, properly interpreted, while Galileo had failed for the much more difficult problem of Saturn. (This Latin note, by the way, may represent the first appearance of the word "microscope" in print. Galileo had called his instrument an occhiolino, or "little eye," and his fellow Lynxes had then suggested the modern name.)
But Stelluti's luck had run out with Cesi's wood, when he invoked the same kind of claim to buttress his errors. Consider a sampling of such statements, following the order of Stelluti's text:
The generation of this wood, which I have
been able to see and observe so many times,
does not proceed from seeds. . . .
The material of this wood is nothing other
than earth, because I have seen pieces of it
[perche n'ho veduto io pezzi] with one
part made of hard earth and the other of
Figure 7 shows a
drawing of a large oval
specimen, which I
excavated myself from
The outer surface of
the other piece appears
to be entirely in wood,
as is evident to the eye
[in the drawing
presented by Stelluti].
Stelluti ends his treatise with a flourish in the same mode; he need not write at great length to Justify his arguments (his entire text only runs to twelve pages), because he has based his work on personal observation:
And this is all I need
to say, with maximal
brevity, about this
material, which I have
been able to see and
observe so many times
in those places where
this new, rare, and
of nature is born.
But Stelluti had forgotten the old principle now embodied in a genre of jokes that begin by proclaiming: "I've got some good news and some bad news." Galileo's empirical method can work wonders. But no faith can be more misleading than an unquestioned personal conviction that the apparent testimony of one's own eyes must provide a purely objective account, scarcely requiring any validation beyond the claim itself Utterly unbiased observation must rank as a primary myth and shibboleth of science, for we can only see what fits into our mental space, and all description includes interpretation as well as sensory reporting. Moreover, our mental spaces embody a complex architecture built of social constraint, historical circumstance, and psychological hope--as well as nature's factuality, seen through a glass darkly.
We can be terribly fooled if we equate apparent sight with necessary physical reality. The great Galileo, the finest scientist of his or any other time, knew that Saturn--Stelluti's personal emblem--must be a triple star because he had so observed the farthest planet with good eyes and the best telescope of his day, but through a mind harboring no category for rings around a celestial sphere. Stelluti knew that fossil wood must grow from earths of the mineral kingdom because he made good observations with his eyes and then ran an accurate sequence backward through his mind.
And thus, nature outfoxed the two Lynxes at a crucial moment of their careers--because both men concluded that sight alone should suffice, when genuine solutions demanded insight into mental structures and strictures as well.
As a final irony, the emblem of Stelluti and Galileo's own society--the lynx itself--had been chosen as an exemplar of this richer, dual pathway. Federico Cesi had named his academy for a wild and wily cat, long honored in legend for possessing the sharpest sight among animals. But Cesi had chosen well and subtly, and for a conscious, explicit reason. The acuity of the lynx arose from two paired and complementary virtues--sharpness of vision and depth of insight, the outside and the inside, the eye and the mind.
Cesi had taken the emblem for his new society from the title page of Giambattista della Porta's Natural Magic (1589 edition), where the same picture of a lynx stands below the motto aspicit et inspicit--literally read as "he looks at and he looks into," but metaphorically expressing the twinned ideals of observation and exPerimentation. Thus, the future fifth Lynx, the living vestige of the old way, had epitomized the richer path gained by combining insight with, if you will, "exsight," or observation. Cesi had stated this ideal in a document of 1616, written to codify the rules and goals of the Lynxes:
In order to read this great, true, and
universal book of the world, it is necessary
to visit all its parts, and to engage in both
observation and experiment in order to
reach, by these two good means, an acute
and profound contemplation, by first
representing things as they are and as they
vary, and then by determining how we can
change and vary them.
If we decide to embrace the entire universe as our source of knowledge and insight--to use, in other words, the full range of scales revealed by Galileo's two great instruments, the telescope and the microscope (both, by the way, named by his fellow Lynxes)--we had better use all the tools of sensation and mentality that a few billion years of evolution have granted to our feeble bodies. The symbol of the lynx, who sees most acutely from the outside but who also understands most deeply from the inside, remains our best guide. Stelluti himself expressed this richness, this duality, in a wonderfully poetic manner by extolling the lynx in his second major book, his translations of the Latin poet Persius, published in 1630. Cesi had selected the lynx for the animal's legendary acuity of vision, but Stelluti added:
Not merely of the exterior eyes, but also of
the mind, so necessary for the
contemplation of nature, as we have taught,
and as we practice, in our quest to penetrate
into the interior of things, to know the
causes and operations of nature . . . just as
the lynx, with its superior vision, not only
sees what lies outside but also notes what
arises from inside.
Stephen Jay Gould teaches biology, geology, and the history of science at Harvard University. He is also the Frederick P. Rose Honorary Curator in Invertebrates at the American Museum of Natural History.
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