The specificity comes from Hooke’s interest in craters not as evidence of the Moon’s imperfect nature but as phenomena in themselves: what, he wondered, created such things? Kepler had suggested that they might be great circular barrows: dwelling places built up by Moonpeople to let them move from the shadows in the east in the long mornings to the shadows in the west in the long afternoons. Hooke saw them instead as expressions of movement not across the surface but through it: of either something going in or coming out.
Through experiment, he found that if he “let fall any heavy body, as a Bullet” into “a very soft and well temper’d mixture of Tobacco-pipe clay and Water… it would throw up the mixture round the place, which for a while would make a representation, not unlike these of the Moon.” Alternatively, if “boyling Alabaster… being by the eruption of vapours reduc’d to a kind of fluid consistence… be gently remov’d besides the fire… the whole surface, especially that where some of the last Bubbles have risen, will appear all over covered with small pits, exactly shap’d like these of the Moon.”
It was for the second, internal, cause that he plumped. The splash-craters made by dropping things into watered-down pipe clay were transient; the bubbled-up pockmarks on the alabaster remained after it set solid: a mark in their favour. The details of their appearance in oblique light was another such mark. “By holding a lighted Candle in a large dark Room, in divers positions to this surface, you may exactly represent all the Phænomena of these pits in the Moon, according as they are more or less inlightned by the Sun.”
Hooke was aware that his analogues might mislead. But what his models suggested, analogues confirmed. Volcanoes such as those of Iceland, the Canaries and New Spain had tops shaped “like a dish, or bason” and raised “great quantities of Earth” around them, which he felt bolstered the case for an internal origin. As to the case for bullets, he saw astronomy as revealing nothing which might hit the Moon.
Hooke’s volcanic account of the Moon held the field for most of the next three centuries, reaching its most fully theorized, and most beautifully illustrated, form in the works of a Victorian industrialist, James Nasmyth. Nasmyth was, from an early age, much taken with volcanoes. On walks around their home city of Edinburgh, his father, a noted landscape artist, had taught him that they were responsible for its dramatically knobbily topography. His father’s friend and benefactor, Sir James Hall, after whom Nasmyth fils was named, was one of the first men of science to try to emulate volcanoes by heating rocks to their melting point to see what lavas he could make.
Most of Nasmyth’s meltings, at least in his professional life, were in foundries; but the link to the world of rocks was not remotely lost on him. In 1840 he took a break from a tour of various European shipyards and arsenals which employed steam hammers and other machines of his company’s manufacture to climb Vesuvius. Having marvelled at the vent at the centre of its crater from as close a vantage point as he dared, he later recalled, “I tied the card of the Bridgewater Foundry to a bit of lava and threw it in, as token of respectful civility to Vulcan, the head of our craft.” When he retired rich at the age of 48, he devoted himself to the studies of the Moon that he had previously undertaken in his spare time. He looked forward to “the tranquil enjoyment which results from the study of one of the Creator’s most potent agencies in dealing with the materials of His worlds, namely, volcanic force.”
“The Moon, Considered as a Planet, a World and a Satellite” (1874), the book that Nasmyth, aided by his friend the astronomer James Carpenter, produced from these studies, worked methodically through the three characterisations of its subtitle. It was the first—the Moon’s nature as a planet—that fascinated Nasmyth most.
As the astronomer Richard Proctor wrote at roughly the same time, the issues “of progress, development and decay” were “the principal charm of… all observational science”. Proctor saw the lack of such changes as a deficit on the Moon’s part. Nasmyth and Carpenter thought them discoverable with the concepts that Victorian science had developed to understand progress, development and decay: evolution—a concept which included, but went beyond, Darwinian natural selection—and thermodynamics, the nascent science of energy, heat and work. The now changeless Moon had previously undergone “a constant progression from one stage of development to the next… a perpetual mutation of form and nature”; it had evolved. And an understanding of that evolution could explain the history of other planets, most importantly the Earth, in new ways.
The book follows the account of the solar system’s origin given by the great French astronomer Pierre-Simon Laplace: a nebula of dust and gas collapsed in on itself because of Newtonian gravitation. As it did so, an enormous amount of potential energy was given up, and the first law of thermodynamics stated that that energy could not just vanish. Instead, it went into heat. As one of the first law’s framers, Julius von Mayer, had put it, the nebula’s collapse was a source of heat “powerful enough to melt worlds”. Nasmyth and Carpenter believed the Earth and Moon to have been born molten and to have solidified from the outside in.*
The Moon cooled from its molten state quicker than the Earth. This was because it was small, and small things cool quicker than big ones, and because it lacked an atmosphere, and so was not kept warm by the greenhouse effect.† Nasmyth’s foundry experiences convinced him that the solid crust must have been less dense than the liquid beneath it, and so as the crust grew it squeezed the molten layers beneath it. Eventually, the pressure below became so great that the crust could no longer contain it; molten lava rushed up to the surface and out into the void beyond it. Extreme pressures, low gravity and a lack of any air resistance provided “conditions most favourable to the display of volcanic action in the highest degree of violence.”
The lava in these eruptions did not just flow down the sides of mountains. It flew tens or hundreds of kilometres into space before falling back to the surface. The eruptions were like parabolic fountains in which water is squirted up from the middle of a pool and comes back down all around its rim. They thus created great circular walls, not single peaks.
This theory explained why, whereas the craters of Earthly volcanoes sat atop mountains, the interior of lunar craters often sat lower than the surrounding plains: as vast amounts of hot rock from the depths shot out into space, the undermined surface subsided as the lava built up all around. It also explained why many craters had solitary peaks at their centre: they were the last gasps of the eruption, no longer able to throw lava tens of kilometres, but still able to build up a mountain in the more subdued Earthly style.
Understanding the Moon’s surface as a function of its history in this way provided a new way of thinking about the Earth. Geology was at the time a “uniformitarian” discipline: it insisted that the past had been sufficiently like the present that through an understanding of the processes in the world today—erosion, sedimentation, volcanism—you could explain all that needed explaining about the past. The cosmic perspective offered by the Moon suggested that the past could have been very different even though the Earth, the Moon and the solar system were all embedded in a cosmos changed by the working out of physical laws.
As well as a prototypical planet in the cosmos, though, Nasmyth and Carpenter also saw the Moon as a satellite of the Earth—a relationship which they believed to be defined by its utility. Considering the Moon as a satellite meant asking what it does for earthlings.
As a source of light, it gets short shrift. For most people, through most of history, this has surely been the Moon’s great importance—bringing light to the night, and to some nights more than others. But to an up-to-date Victorian, his streets lit by gas and his house lit by paraffin, moonlight was not what it had been as recently as a century before, when an earlier generation of industrialists and inventors, the members of the Lunar Society of Birmingham, met at the full Moon because it made it easier to ride home. For Nasmyth, moonlight was all very well for poets, painters and peasants. Indeed, it should exci
te “our warmest admiration”. But it wasn’t really up to snuff: it was changeable, fugitive, partial, imperfect and of secondary importance. For men of action, tides were the measure of the Moon.
“Rest and stagnation are fraught with mischief,” says the bustling Victorian businessman. “Motion and activity in the elements of the terraqueous globe appear to be among the prime conditions in creation.” The Sun provides this highly desirable motion and activity by driving the winds. The Moon does the same for the waters, cleaning out the corruption of estuaries such as those of the Thames and Mersey. It is “our mighty and ever active ‘sanitary commissioner’”.
Tides provide not just cleanliness: they aid in commerce, too. The extra lift outgoing tides provide to ships and barges leaving port saves a city like London thousands of pounds a year, maybe millions. And in time they will provide ever more power. Britain’s coal—“bottled sunshine”, as the book puts it—is inevitably going to run out. The mechanical power of the tides, transformed into electricity and passed down wires to the industries that need it, could become the nation’s new prime mover.
Light and sanitation are not the only satellite services; navigation and timekeeping get a look in, too. And despite Nasmyth’s no-nonsense business sense, not all the uses of the Moon are utilitarian. There is something more elevated—its deathliness teaches us to esteem the habitable Earth even more highly. And it reveals the truth of an earlier age in a way nothing else can do. The foundryman’s eye sees in it a planet “with all the igneous foundations fresh from the cosmical fire, and with its rough-cast surface in its original state, its fire and mould marks exposed to our view.” The scientist’s mind rejoices at the sight.
One of the two founding documents of British geology—and its uniformitarian mindset—was James Hutton’s “Theory of the Earth” (1788). Those perambulatory discussions of the crags of Edinburgh would have made copious reference to the great man; Nasmyth’s namesake James Hall had been Hutton’s leading disciple. The most famous line from Hutton’s “Theory”, with its vistas of the untiring grinding-down of mountains and the slow resurgence of seabeds into the sky, is its last one: “The result, therefore, of our present enquiry is, that we find no vestige of a beginning, no prospect of an end.” On the Moon, though, write Nasmyth and Carpenter, “its pristine clearness unsullied, every vestige [is] sharp and bright as when it left the Almighty Maker’s hands.” The Moon, frozen at an earlier stage of planetary evolution, reveals to its student what the eroded Earth cannot. The vestige of a beginning, lost on Earth, is preserved in the sky, ancient and new.
THE BOOK’S IDEAS ARE FASCINATING; ITS LANGUAGE AND ASIDES are often a delight. But what Nasmyth’s work is best remembered for is not its words or arguments but its illustrations: in particular, its photographs.
Almost none of them, surprisingly, are photographs of the Moon. Though astronomers were using photography by the 1860s, their pictures of the Moon were not terribly good, especially not for bringing out the features that Nasmyth cared about most. Yet photographs were setting a new standard for fidelity in representation, for recording the specific contents of the world as they were. They were of the moment. So Nasmyth photographed the Moon as he imagined it.
Nasmyth’s father, having made sketches of landscapes outdoors, would retreat to his workshop and make clay models of what he had seen based on the sketches and his memories. His son thus learned to treat modelling as a way of thinking, one which placed the skill and experience of hand and eye at the service of reason and analogy. And that was how he made his Moon visible to the world. He sketched, he modelled, and then, having mastered the techniques of photography expressly for this end, he photographed the models in strong, oblique light rather like the one with which Hooke observed his cratered alabaster. In doing so, he probably influenced how the Moon was seen by others more than anyone else between Galileo and the 1960s.
The lunar drawings Nasmyth had made earlier in his career were both beautiful and widely appreciated—he showed them to Queen Victoria herself—but his modelled photographs had a sharpness that went beyond them, especially in the depth of their shadows. Many of the pictures look straight down onto specific features of the Moon. Some, such as his picture of Theophilus, Cyrillus and Catharina, a trio of similarly sized large craters which is thrown nicely into relief when the night-edge passes them about five days after the new Moon, can, at first glance, be mistaken for photos of the real thing.*
There are also pictures “taken” obliquely, or from the standpoint of an observer standing on a lunar plain. One shows the Sun eclipsed by the Earth, its atmosphere a fierce red ring. Another, switching points of view, shows the Bay of Naples in the same straight-down view as used in the pictures of the Moon, the better to draw out Nasmyth’s analogy between its craters and those of the Campi Flegrei and Vesuvius (features which, it must be admitted, look a lot more lunar in Nasmyth’s model than they really do from orbit).
A few move into pure analogy. Nasmyth’s ideas about the wrinkling that the Earth’s slower-than-lunar cooling imposed on its surface are strikingly illustrated with pictures of long-since-picked apple and an old man’s hand (his own). A glass bulb cracked by a small expansion demonstrates the mechanism by which he believed the rays emanating from Tycho and other bright craters were made.
In Jules Verne’s “Autour de la Lune” (1870; “Around the Moon”), the sequel to “De la Terre à la Lune” (1865; “From the Earth to the Moon”), Barbicane, the leader of the expedition, looks down from orbit in wonder at Tycho’s rays. Michel Arden, a poet along for the ride, says that they look like cracks made in glass by a thrown rock—perhaps, in this case, by a comet. Barbicane pooh-poohs the idea; the force must have come from a shock within. This is not just obvious to his educated eye. It “is the opinion of the English savant, Nasmyth”.
“No fool, that Nasmyth,” replies the assenting poet.
This is just one of the ways in which the Moon Verne’s travellers circle is Nasmyth’s Moon; one of mountainous annular volcanoes, lofty impassable ramparts and little else. In particular: no air, no streams, no woods, no life. Verne’s book is the first story of the Moon to find it uninhabited. It may have been inhabited once—Arden sees what he takes to be a ruined city and aqueduct—but now, the travellers agree, it is almost certainly dead.
What about the Moon is interesting, if the Moon is dead? Getting there. Verne’s original book is the first Moon story in which the technology that gets explorers on their way is more interesting than their destination. The ability to reach the Moon, Verne says, marks the point at which humans have become a power of truly planetary significance. In a way Nasmyth would doubtless have appreciated (alas, I know of no record that he read the book he influenced), the casting of the great 900-foot cannon that sends Arden, Barbicane and Captain Nicholl to the Moon is explicitly compared to a volcanic eruption:
A savage, wandering somewhere beyond the limits of the horizon, might have believed that some new crater was forming in the bosom of Florida, although there was neither any eruption, nor typhoon, nor storm, nor struggle of the elements, nor any of those terrible phenomena which nature is capable of producing. No, it was man alone who had produced these reddish vapors, these gigantic flames worthy of a volcano itself, these tremendous vibrations resembling the shock of an earthquake, these reverberations rivaling those of hurricanes and storms; and it was his hand which precipitated into an abyss, dug by himself, a whole Niagara of molten metal!
The launch is grander still:
An appalling unearthly report followed instantly, such as can be compared to nothing whatever known, not even to the roar of thunder, or the blast of volcanic explosions! No words can convey the slightest idea of the terrific sound! An immense spout of fire shot up from the bowels of the earth as from a crater. The earth heaved up, and with great difficulty some few spectators obtained a momentary glimpse of the projectile victoriously cleaving the air in the midst of the fiery vapors!
The travel
lers, Verne tells us, have “placed themselves beyond the pale of humanity, by crossing the limits imposed by the Creator on his Earthly creatures.” So, it seems, had the industry that made that transgression possible, a human power no longer distinguishable from the powers of the Earth itself.
NASMYTH’S SENSE OF THE MOON AS A KEY TO UNDERSTANDING the Earth’s evolution still rings true. So does his vision of planets which, like steam engines, are shaped by great flows of energy and the laws of work and heat those flows obey. He got some remarkable details right, too, suggesting that bacteria—then, in the form of “germs”, a very new-fangled concept—might be able to survive in space when all other forms of life could not or that the appearance of the Earth from the Moon would be dominated by ever-shifting bands of cloud, not continents, or that tidal barrages could produce large amounts of electricity. But he got the Moon itself profoundly wrong, both in the general way that he explained it and in one specific way he envisioned it.
To take the second first: in order to produce the sort of shadows he saw through his telescope—and, one cannot help but think, to satisfy his own liking for the craggy and picturesque—Nasmyth made his lunar mountains very steep and jagged. In so doing he set the visual template for future renditions. The great 20th-century American astronomical artist, Chesley Bonestell, made his Moons just as craggy when he painted them for magazines like Life, Scientific American and Collier’s, or as backdrops for the film “Destination Moon”. So did those whose drawings drew on Bonestell’s, as the Belgian cartoonist Hergé’s did when he sent his boy reporter Tintin to the Moon. And why should the Moon’s mountains not be craggy and magnificent? There were no winds, no rains, no glaciers to erode them. They should be raw and sharp.
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