Seeing Further (20 page)

Yet for all this, Cavallo was a passionate balloon enthusiast. He recorded and analysed all the significant flights, both French and English, made from the Montgolfiers’ first balloon at Annonay in June 1783 to Blanchard and Jeffries’ crossing of the Channel in January 1785. He distinguished carefully between hot-air and hydrogen balloons, and their quite different flight characteristics. He looked in detail at methods of preparing hydrogen gas, noting that Priestley had come up with one that used steam rather than sulphuric acid. He also examined the different ways of constructing balloon canopies from rubber (‘cauchouc’), waxed silk, varnished linen and taffeta.

In a longer perspective, he stressed the astonishing speed of aerial travel over the ground – ‘often between 40 and 50 miles per hour’ – combined with its incredible ‘stillness and tranquillity’ in most normal conditions. This he thought must eventually revolutionise transport and communications, even if the moment had not yet arrived. He pointed out that in achieving altitudes of over two miles, balloons opened a whole new dimension to mankind’s observations of the Earth beneath. Man’s growing impact on the surface of the planet became visible from the air for the first time, as did the vast tracts of the Earth – mountains, forests, deserts – yet to be traversed. Above all he stressed that the full potential of flight had not yet been remotely explored.

Cavallo considered the whole range of possible balloon applications. But he finally and presciently championed its relevance to the infant science of meteorology:

It was largely due to Cavallo’s book that, a decade later, ballooning received a signal acknowledgment and consecration. The third edition of the hugely influential
Encyclopaedia Britannica,
published in 1797, for the first time recognised the existence of ‘Aerostation’. It described it with all due formality as ‘a science newly introduced to the Encyclopaedia’, and gave it a comprehensive article of fourteen pages. This included two full spreads of diagrammatic illustrations, showing every known kind of aerostats that would actually fly. Almost all the material was drawn, unacknowledged, from Tiberius Cavallo.

The editors of the great
Encyclopaedia
made one symbolic gesture. They placed as the frontispiece to the opening volume of the new edition a prophetic engraving. It showed a traditional gathering of ‘natural philosophers’ in a Roman forum, arrayed in classical togas and surrounded by pillared Doric temples. (Could they have intended a sly reference to the
Royal Society?) They then introduced one striking anachronism. High overhead, a hydrogen balloon (complete with wings) sails imperiously into some unknown future.

Such prophetic dreams would soon be taken up by a new generation of British aeronauts, such as James Sadler and Charles Green. But as for Sir Joseph Banks PRS, now perhaps made more earth-bound by his knighthood, aerostation virtually disappears from his letters after 1790. When in January 1800 he received a charming inquiry from Ireland suggesting a scheme to build a balloon railway beneath a ‘mile-long covered gallery’ at Greenwich, he replied with barely a sigh: ‘The Royal Society have no Funds destined for the Execution of Projects so Expensive as yours must be; nor indeed have they in any one instance
interfered
in the business of Aerostation.’

O
BSERVATION WAS A CRUCIAL FOUNDATION FOR THE NEW SCIENCE. IN BIOLOGY, THAT MEANT THE CLOSEST EXAMINATION OF SPECIMENS. KEEPING THEM, SO OTHERS COULD REFINE THE OBSERVATIONS YEARS, DECADES, OR EVEN CENTURIES LATER, PROVED TO BE JUST AS IMPORTANT, AS RICHARD FORTEY EXPLAINS
.

Safely stored behind the scenes at the Natural History Museum in South Kensington is a slightly twisted vertebrate skeleton preserved on a slab of creamy white limestone. This particular specimen was discovered in quarries near Solnhofen in southern Germany in 1861. The fine limestones of Solnhofen are ideally suited to making lithographic stones, and in the nineteenth century lithographs provided one of the most important means of book illustration – indeed lithographic stones of this quality are still in demand by artists today. Vast quantities of this lithographic limestone of Jurassic age – about 150 million years old – have been taken out of opencast workings, where the rocks can be split into convenient slabs a centimetre or two thick; the German word
plattenkalk
appropriately describes their lithological character. On many of these flat-surfaced pieces of rock, fossils are laid out like gifts on a salver.

Some Solnhofen fossils are rather common, such as those of delicate little sea lilies. Others are both rare and more spectacular. There are a great variety of fish species known nowhere else, for example. The fossil horseshoe crab
Mesolimulus
provides evidence that its living relatives breeding each year along the Atlantic coast of America have changed little over tens of millions of years. Delicate flying reptiles – half a dozen species or so of pterodactyl – testify by contrast to creatures that have vanished from the Earth for ever. A few species of dinosaur are known, of the most delicate sort
(Compsognathus)
, and quite unlike the monsters of popular imagination. Insects include dragonflies
(Aeschnogomphus)
whose every wing-vein is visible as delicate tracery. All these creatures are preserved in rocks which originated as tacky muds flooring a lagoon that lay offshore from a richly biodiverse habitat. Such special circumstances sampled and preserved a much wider variety of organisms than the usual fossil locality, and the wide range of fossils provides a rare window into an entire habitat from a very different world. Yet if the remains were not kept carefully in museums all
this evidence of past life would perish, and new generations of children and scholars could not interrogate the past. Local museums at Eichstätt and Solnhofen fulfil that function for those who would come to Bavaria and marvel at its geological treasures. But some of the specimens from the Solnhofen limestone have a relevance that extends far beyond the reconstruction of the late Jurassic scene, and these specimens are treasures in the collections of museums around the world. None more so than that specimen – a mere 35 cm at its longest – safely curated in the Natural History Museum in London.

For this is the first example ever discovered of the early bird
Archaeopteryx.
It remains one of the most important specimens in the British national collections. The next complete fossil bird of the same species – the so-called Berlin specimen – was found sixteen years later. It would be difficult to overstate the importance of this London specimen of
Archaeopteryx
in the history of biology.

First, the date of its discovery is only two years after the publication of
The Origin of Species,
the sesquicentenary of which we celebrated in 2009. Charles Darwin famously described what he called ‘difficulties on theory’ in that work, where he anticipated a number of criticisms that he expected his great idea to encounter. Prime among these was ‘the rarity or absence of intermediate forms’ in the fossil record. Second, the detailed scientific description
of Archaeopteryx was
an accomplishment of Richard Owen in 1863; he was later to become first director of the Natural History Museum. Owen was no Darwinian, but he was an able anatomist. It must have proved anathema to him when
Archaeopteryx
was recruited as probably the best example of an ‘intermediate form’ and one that had turned up with the impeccable timing usually associated with a good piece of theatre. Its amalgam of reptilian and bird features (feathers and wishbone among them) was a striking vindication of the notion of descent with modification, and a rebuttal to those who might wonder how it was possible for animals to make the transition from earth to the skies.

In this sense
Archaeopteryx
became a kind of talisman for evolution. Owen was enough of a ‘Museum man’ to ensure that this fossil was safely curated, and part of any museum’s function is just that – to protect material regardless of the current explanations of its importance. The old bird has now been joined by half a dozen or so subsequent examples worldwide, but its importance has not diminished over the years. Periodically, it has been taken out from storage and re-evaluated. Sir Gavin de Beer described it in great detail in 1954. Twenty years later more bits of it were manually prepared, and new details revealed, and in the last few years the brain case of the early bird has been CAT-scanned and its endocast reconstructed. All these endeavours have served to confirm the transitional nature of
Archaeopteryx
– but have also confirmed that in most important functional respects it is closer to the birds than to the dinosaurs. This in turn has contributed to the debate about whether birds descended from one particular group of dinosaurs: most palaeontologists nowadays concur that they did. One might say that the
meaning of Archaeopteryx
has changed, while the information that has been extracted from this specimen (and other new discoveries) has increased fitfully as scientific hypotheses have shifted.

I begin with the London specimen of
Archaeopteryx
because it is an emblem for the importance of collections in science. Collections provide the ground truth on which hypotheses are built. Physics has laboratories; systematic biology has collections. It would be misleading to claim that the millions of specimens stored in cabinets and bottles in the galleries of national natural history museums are all, individually, as important as the type specimen
of Archaeopteryx.
But well localised, properly documented natural history archives have been, and continue to be, central to understanding many kinds of scientific questions: the course of evolution; the relationships between animals and plants (the ‘tree of life’); biogeography and biodiversity; how climate change has affected the biota. Human memories are short and inaccurate. Our shifting perceptions need to be tested against archives which are – as near as possible – permanent records of the fauna and flora.

This concept of collections developed or evolved rather like those organisms kept in drawers or herbaria. There is evidence that humankind made collections from the earliest times, if claims about pierced snails and tusk shells from Africa are to be believed. These first collections were assuredly made for ornament, but humans evidently had a taxonomic eye from the outset, by picking out matching individuals belonging to a single species. Development of a ‘working taxonomy’ – distinguishing edible from poisonous plants, for example – is clearly of adaptive value. Collections made for cultural purposes accompanied early civilisations, and Adrienne Mayor has argued that fossil mammal collections made from the Cenozoic rocks of the Mediterranean region were displayed in Classical times as concrete evidence of the battles between races of giants and men: evidence of a kind, but mostly spectacle.