Stories in Stone

by David B. Williams

  It is easy to see why early gravestone carvers chose slate. They could split the slate into slabs and could cut the stone with ease and with exquisite detail. Who knows if the carvers knew how well slate resisted erosion, but they probably would be surprised and pleased that you can still discern individual teeth on Elizabeth Pain’s winged skull. Furthermore, you can make out the remaining parts of the whorl on the broken right shoulder, even though only the top layer of slate remains, and there is no doubt that lions populate the escutcheon.

  The tripartite headboard shape of Pain’s tombstone is a classic style of gravestone from Puritan New England, akin to what biologists call an indicator species. Whenever you see a headboard-shaped slate grave marker, you can almost guarantee that you are in a former stronghold of Puritans. In addition to the bed of death connection, a tripartite shape represented the arched doorway that the soul passed through on its way to eternity. Variations on the theme occurred, but for the most part the headboard remained popular to around 1800, when a neoclassical revival arrived and gravestones became taller, sleeker, and more three-dimensional.

  A winged skull also appeared widely on gravestones during the Puritan era. Like the headboard shape, winged skulls told of death, arguably the central preoccupation of an average Puritan’s life. They died young. They saw death regularly. They heard about death weekly from their preachers. Placing a winged skull prominently on grave markers reminded all who visited that their life would end soon, too.

  And if Elizabeth Pain’s visitors didn’t get the point of the skull, they should at least have understood the winged hourglass. Time flies, your time is short. Subtlety was not a strong point of Puritanism.

  Below the winged skull, Pain’s gravestone reads “Here Lyes Ye Body of . . .” The words refer specifically to the mortal remains; yet another reminder that the body and not the soul was the focus for the Puritans. Although Pain’s gravestone lacks an epitaph, many stones had ones that emphasized rot and decay, or as Benjamin Franklin wrote in 1723 in his mock epitaph, your body will be “food for worms.”17 No wonder modern people have such a gruesome image of the Puritans.

  The imagery, slate, and wording of Pain’s tomb were the common language of burial grounds throughout the 1700s, but with the decline of Puritanism and corresponding rise of more liberal religious viewpoints, change spread across the world of death. Less forebidding winged faces or cherubs replaced the ominous winged skulls, followed in the early 1800s by the rise of the urn-and-willow design, symbolic of more secular beliefs. In addition, “In Memory of” began to supersede “Here Lyes Ye Body of,” as the focus of death turned more toward the mourner and away from those who died.

  These religion-influenced changes coincided with overcrowding and poor burial practices at Boston’s burying grounds. The latter problem led to grave robbers regularly poaching parts and bodies for medical studies and to diseases spreading with the malodorous miasmas wafting from the dead. New religious outlooks, a concern with sanitation and safety, and the rise of neoclassicism ultimately are made manifest in the development of a new type of burial ground, the cemetery.

  Boston’s elite, many of whom were helping pay for the erection of Bunker Hill Monument, established Mount Auburn Cemetery in 1831. Located four miles from Boston, Mount Auburn consisted of seventy-two acres of trees, dells, ponds, and wetlands. It was beautiful, free of bad air and grave robbers, and organized so that people could purchase lots, everything the Boston burial grounds were not. Reflecting the new religious views, Mount Auburn was a landscape where “death would seem disrobed of half its terrors,” or so wrote an early visitor.18

  Mount Auburn’s founders took two additional tacks in their goal of exorcising the ghosts of Boston’s old burial grounds. First, they banned perpendicular slab gravestones. Instead, they wanted three-dimensional monuments, such as sarcophagi, obelisks, mausoleums, and columns, and their allusions to antiquity. The founders also prohibited the use of slate; they considered it stiff, ungainly, and gloomy. And who wanted to be reminded of those dreary Puritans?

  What did the founders replace slate with? Boston’s Brahmins preferred marble, despite its reputation for poor durability in a cold climate. In contrast to slate and its connection to the Puritan’s dour imagery of death, marble “suggested the purity of heavenbound souls and the assurance of salvation provided by liberal religion.”19 Unable to compete with purity and salvation, utilitarian slate’s reign in New England graveyards came to an end.20

  In February 2008 I returned to my old elementary school for the first time in over thirty years. Stevens was still an elegant Georgian-style building, but a new addition to the north marred the wonderful symmetry of old. Entering the front doors, I discovered that the wide wood steps that once led up to the second floor were gone. I stayed on the ground level and entered the school’s office, what in my day had been the boiler room. I checked in, put on my Visitor button, and headed out in search of the blackboards of my youth.

  As I got oriented, I found a stairway. It was much as I remembered, except now I noticed how thousands of little feet had worn a low spot in each stair about one foot from the banister. Someone, probably a well-meaning adult, had also placed metal nubs on the banister to prevent kids from sliding down. At the top of the stairway the floor of the hall was still wood and looked to be original, with some planks running twenty feet long or more. Dark wood still framed the doorways to each classroom, but the little cloakrooms where we hung our coats had been removed.

  I stuck my head in one classroom. The blackboard was gone. I looked in another room. Also empty of slate. A teacher wandered by and I asked her about the blackboards. “They were all replaced when the school was remodeled in 1999,” she said. “They were real slate and I have about twenty small pieces of it at home. I don’t know what I am going to do with it.”

  The Seattle school district, like many across the country, has been phasing out blackboards for years. Dust is to blame. It’s bad for kids because the fine particles exacerbate respiratory problems such as asthma and allergies. It’s bad for computers because chalk dust gets into the keyboards and other sensitive parts. It’s bad for fashion because chalk dust gets on clothes and in hair.

  Every classroom at Stevens now has a whiteboard instead of a blackboard. Teachers use pens instead of chalk, which gives them the luxury of multiple colors, in contrast to earlier monochromatic eras of white chalk, or perhaps yellow. Pens provide better contrast and higher visibility and don’t produce all of that nasty dust that coated hair and clothes. Nor can anyone annoy his or her classmates by running their fingernails down the blackboard.

  Despite the numerous benefit of pens over chalk, whiteboards are far from ideal. Chalk dust can be an irritant to some people, but generally the large particles settle out of your nose before they have a chance to get into your lungs; whiteboard cleaners, though, produce toxic fumes. The cleaners come with warning labels. Another drawback to whiteboards is the residue of writing that doesn’t wash off, no matter how much cleaner you use. And when someone uses a Sharpie pen by accident, you cannot erase it from a whiteboard. Furthermore, half the time you try to use dry-erase pens they don’t work because they have run out of ink. Then what do you do? Toss them in the garbage so they can end up as landfill. No one ever has to doubt whether a piece of chalk is usable, and when it becomes too small to write with, you can just carry it outside and bury it. It will soon degrade and disappear without a trace.

  As I wandered the hallways at Stevens, I couldn’t help but wonder if today’s students are missing out. Where once they could have continued the centuries-old tradition of employing fossil sea critters to write or draw on a metamorphosed slab of fine-grained marine sediment, now they write on petroleum-based, plastic whiteboards with an odoriferous, chemical-filled pen. In a society where our failed connection to nature surely has contributed to our failed understanding of human impact on the land, the loss of slate and chalk is one more example of how we are taking nature aw
ay from children and replacing it with something artificial. Perhaps this connection was the most utilitarian aspect of slate and now it, too, is lost.

  10

  “AUTUMN 20,000 YEARS AGO”—

  ITALIAN TRAVERTINE

  After they had noted what a profusion of resources has been begotten by Nature, and what abundant supplies for construction have been prepared by her, they nourished these with cultivation and increased them by means of skill and enhanced the elegance of their life with aesthetic delights.

  —Vitruvius, Ten Books on Architecture, book two

  He’ll study weird stuff that grew in his sink last week, for instance, bird droppings, a bit of arterial plaque, or his wife’s cataract. His instincts are amazing, though. No matter how oddball, the things Dr. Folk chooses to look at often end up teaching us something about rocks.

  —Dr. Kitty Milliken, University of Texas

  GEOLOGISTS DO NOT normally receive standing ovations when they make presentations at meetings. Typically, attendees clap politely, ask a few questions, and then the next presenter walks to the podium and begins his or her talk. In October 1992, however, geologist Robert Folk received a standing ovation for his fifteen-minute presentation at the annual Geological Society of America meeting in Cincinnati. He had titled his talk “Bacteria and Nannobacteria Revealed in Hardgrounds, Calcite Cements, Native Sulfur, Sulfide Minerals, and (yes) Travertines.”

  Folk’s talk focused on his work from calcite-rich rocks in Italy, as well as the Bahamas, Utah, and Florida. He began by describing how he had used hydrochloric acid to etch, or eat away, surface material to reveal undisturbed layers of calcite. With this novel etching technique, Folk reported that he had been able to exhume microscopic (requiring greater than 20,000 magnification) bacterial bodies from the rocks, primarily from a type of limestone called travertine, and that the microbes had “emerged from the calcite like cadavers on Judgment Day.”

  He called his microbes “nannobacteria,” in reference to their nanometer-scale size. (Folk prefers his double-n construction, but most nongeologists prefer “nanobacteria” or the less controversial—read as no indication of life—“calcifying nanoparticles.” Folk’s use of “nannobacteria” still rankles many biologists.) No one had ever reported and shown photographs of such microscopic organisms. Prior to Folk’s work, the smallest recorded bacteria stretched 200 nanometers in diameter, or .005 the diameter of the proverbial head of a pin. In contrast, some of Folk’s nannobacteria were as small as 25 nanometers or .001 the volume of previously described bacteria, although many ranged up to 150 nanometers. The bacterial bodies resembled “ears of corn” and had “great fossilization potential,” he concluded.

  Chris Romanek was one of those who attended Folk’s 1992 talk. Now a geologist at the University of Georgia, Romanek was then a postdoctoral fellow at NASA. “I had sort of wandered in, not knowing who was speaking,” said Romanek. “I remember he was talking about using an SEM [scanning electron microscope] to see microorganisms in these travertines from Italy. I thought this is kind of interesting.”1 When Romanek finally learned who was speaking, he knew at once who Folk was: “I had used his textbook in college.”

  First published in 1974, Petrology of Sedimentary Rocks has long been a bible to geologists studying the rocks that make up 80 percent of Earth’s crust, including limestone, sandstone, and coquina. Out of print for years, it is now available online from the University of Texas in Austin, where Folk taught geology from 1952 until his retirement in 1990. Folk wrote the book to supplement lectures and labs that he gave in Austin and based it on lectures he had attended at Pennsylvania State College, where he received his bachelor’s, master’s, and doctoral degrees. The book is so legendary that geologists have been known to come up to Folk at geology meetings and ask him to autograph their dog-eared copies.

  “Folk’s talk got me thinking about limestones and how they would be conducive for trapping and fossilizing microbes,” said Romanek. Although his specialty was carbonate rocks such as limestone that contain the minerals calcite, dolomite, and aragonite, he had not thought about this connection between physical and biological processes in their formation. It was a connection that would have profound implications for Romanek’s research.

  Thirteen months later, Folk’s talk came back to Romanek when his colleague at NASA, David Mittlefehldt, asked him to look at pictures of orange blobs on a meteorite from Mars. Mittlefehldt told Romanek that the microscopic, pumpkin-colored rosettes were carbonates. The photographs stunned Romanek, who had never seen carbonate minerals on a rock from outer space. He immediately asked Mittlefehldt if he could get a sample from the rock, which had been found in Antarctica in 1984. Romanek believed he had the tools, primarily through Folk’s etching technique, to tease out the answer to the underlying question of how carbonates—minerals often associated with water and living organisms—developed on a potato-sized rock that had traveled millions of miles across space.

  After receiving a pinhead-sized chip of the Martian meteorite, Romanek etched his sample with acid and began to probe the rock. Looking under the SEM, Romanek found a screen filled with bacteria. He couldn’t believe what he was seeing, life forms on a rock from outer space. Unfortunately, he wasn’t seeing microscopic ETs; instead, Romanek was looking at Texas bacteria. The microbes that polluted his sample came from unfiltered water he had used to dilute his etching acid. He tried again, this time with filtered water, and again saw features that looked like relicts of bacterial organisms through the SEM. The rod-and ball-shaped structures resembled the nannobacteria Folk had described from travertine at his 1992 Cincinnati talk.

  Romanek knew that he had found something extraordinary within the meteorite’s orange blobs. Since the rods and balls were discovered within carbonates—minerals known to form via biologically induced deposition—the structures could be organic remains. For the next two years, Romanek and his fellow researchers at NASA probed, lasered, and scoped the meteorite to determine whether Romanek’s initial observations were correct. They also reviewed Robert Folk’s extensive work on Italian travertine, in particular a paper he published in 1993 that showed two dozen photographs of nannobacteria.

  On August 7, 1996, NASA astounded the world when they reported what Romanek and his colleagues had discovered in their Martian meteorite from Antarctica. The 4.5-billion-year-old rock, known as Alan Hills 84001 (ALH84001), contained evidence for life on Mars. Chris Romanek’s observations on nannobacteria-generated carbonates were central to NASA’s argument. “If I had not seen Bob Folk’s talk, I wouldn’t have thought to do what I did,” said Romanek. “His work definitely kick-started the whole NASA project.” And Folk’s work all started with travertine, a building stone quarried in Italy for more than two thousand years.

  Roman architect and writer Marcus Vitruvius Pollio may never have given a fifteen-minute-long talk at an annual meeting, but like Robert Folk, Vitruvius was a close observer of Italy’s sedimentary rocks. In his landmark De Architectura, or Ten Books on Architecture, he devoted his second book to building materials. “I thought that I should expand on their varieties and the criteria for their use, as well as what qualities they have in building, so that when this information is known, those who are planning to build will avoid mistakes and assemble supplies suitable for buildings,” wrote Vitruvius sometime between 31 and 27 BCE.2

  Vitruvius based his work on empirical investigations he made of the building stones quarried near Rome. In the category of soft and yielding rocks, he included the olive gray Tufo Lionato erupted from the Al-ban Hills southeast of Rome, and Tufo Giallo della Via Tiberina (yellow tuff from the Tiber Road), erupted from Monte Sabatini, north of Rome. Tuff is rock composed of volcanic glass fragments, crystals, and rock fragments deposited by pyroclastic flows produced by violent eruptions of magma. In Rome tuff forms resistant layers in the city’s celebrated seven hills, one of which—Palatine—provided a source for building material in the fifth and sixth centuries BCE.
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br />   Conversely,Vitruvius’s hard, enduring stones correspond to lava flows that crop out near Rome. Roman builders often used these lavas for paving stones. They still pave many streets in the Eternal City. Locals call the three-inch-square paving blocks San Pietrini, “little Saint Peters,” playing on St. Peter’s role as the rock of Christianity. Vitruvius also described rocks of moderate durability, including travertine.

  Travertine is a sedimentary rock rich in calcite and the related mineral aragonite. Layered, dense, and well-cemented, travertine forms primarily in hot springs. The Romans used it as early as the second century BCE for voussoirs to strengthen the Pons Mulvius, which spanned the Tiber. They quarried most of their travertine in Tibur, now Tivoli, about twenty miles east of Rome. During Vitruvius’s day, travertine was known as Lapis Tiburtinus, “stone of Tibur,” later shortened to tiburtino and corrupted to travertino, travertine in English. Modern quarries at Tivoli supply most of the travertine used in the building trade; it is the most commonly used and commercially valuable building stone in the world.

  Although the Roman tuffs had the virtue of being easily worked, Vitruvius wrote that “if they are put in open, uncovered places, then once they have been saturated with ice and frost they crumble apart and dissolve. Likewise, along the seashore they will wear away, eaten by the salt.” In contrast, travertine “endure[s] every strain, whether it be stress or the injuries inflicted by harsh weather.” To deal with the weaker tuffs, Vitruvius recommended builders quarry the stone in summer, let it sit in the open for two years, use only the best, and dump the crappy stone in with foundations. Builders could further protect tuff from water by covering blocks with plaster or by placing travertine on top of the blocks.