Prof. Florence R. Sabin’, the Johns Hopkins colored waxes of the Zieglers’ models are there is a ubiquitous stratospheric haze anatomist. The project was so complex that fluorochromes lighting up the three-dimen- that totally hides the surface at visible Sabin spent seven weeks with Ziegler work- sional patterns of gene expression or wavelengths. ing on the models. It is clear from Sabin’s protein distribution; there are websites National Aeronautics and Space letters home that the process of modeling with three-dimensional representations of Administration (NASA) Headquarters, illuminated her understanding of the three- embryos that can be rotated. And yet, for all noticing these developments, sponsored dimensional of the brain. These, and almost their realism, these images on a monitor the organization of a scientific all of the models were associated with cannot compare with the glories of the workshop, and later ones devoted to the publications in learned journals, lending sci- Zieglers’ work. My next visit to Cambridge entire Saturn system. In 1980, the close entific authority to what might have been will include a detour to the Department encounter of Voyager I yielded a mass of considered merely a commercial venture. of Anatomy to see some of the models in new information, and verified that the sur- Ziegler was a physician and considered him- real life. face cannot be photographed at the visible self a part of the academic community rather wavelengths to which the camera is sensi- than an artisan who made his living making Jan Witkowski tive. All this information, discussed in models. Indeed, he was rewarded with many subsequent meetings, finally led an honorary degree from the University to the launch of the Cassini– of Freiburg. mission, with the large Cassini orbiter Hopwood describes Gustav Born’s Lifting Titan’s Veil: Exploring the the responsibility of NASA, and Huygens Giant Moon of Saturn method of making models that translated (the Titan entry probe) that of the European by Ralph Lorenz and Jacqueline Mitton serial sections of embryos into serial slices Cambridge, 2002. £19.95 Space Agency (ESA). of wax that could be assembled to make a (viii + 260 pages) ISBN 0521794583 Most of these events, and many more whole, which reduced the amount of subjec- recent ones, are recounted by Lorenz and tive interpretation required and made the Mitton. The nature of Titan and its atmos- process more mechanical. Interestingly, a phere, as we understand them today, are similar process was followed by the early well described. An interesting feature of the protein crystallographers who traced the book is an occasional piece ‘Ralph’s Log’, electron density maps onto clear sheets of in which he describes some of his experi- plastic, which were then stacked on one ences studying Titan as an ESA engineer, as another. a graduate student or in designing and It is unfortunate that Hopwood’s writing building one of the instruments now flying is not always as stylish as the images in the aboard the Huygens probe. All the material book and some sentence constructions are is at the level of an average reader, but it is hardly felicitous; for example, ‘Ziegler had also interesting and useful to the expert. The a certain status, then, though perhaps no book is well illustrated, and there is an better than as a drawing teacher he would Saturn’s satellite Titan is larger than the excellent color section showing, among have enjoyed…’ or ‘With a new generation planets Mercury and Pluto and is distin- other things, recent images of the surface of modellers in place, it is here that in the guished by a nitrogen atmosphere denser obtained from the ground or the Hubble next chapter we return’. The Whipple than that of the . The satellite was dis- Space Telescope. These are obtained by Museum in Cambridge has produced a very covered by Huygens in 1655, and in 1908 using wavelengths in the near infrared attractive book but it is a pity that the size was observed by Comas Solà to be limb at which there is a hazy view of Titan’s of the font is rather smaller than older read- darkened, unlike any of the Galilean satel- surface. ers will like, and it is regrettable that lites of Jupiter. The inference was soon There are excellent chapters on the dis- there is not an index. On the other hand, made that there was a dense atmosphere. covery of Titan and up-to-date ones on the using the footnotes is much easier than Kuiper took the first near-infrared spectra nature of the atmosphere and surface. The usual because they are numbered consecu- in 1944, and found unmistakeable evidence last two describe the Cassini–Huygens mis- tively through the book, rather than chapter for methane. But real excitement about the sion, destined to arrive at Saturn in 2004 for by chapter. atmosphere did not flare up until 1972, several years of orbital operations and Hopwood discusses the decline of the when Morrison, Cruikshank and Murphy many close encounters with Titan. There is models – how there was a move away from applied newly developed instruments for more detail about the experiments on the detailed morphological studies of develop- infrared measurements and found that Huygens probe than on the Cassini orbiter, ing embryos. This became ever more pro- Titan’s thermal spectrum is utterly unlike and the Cassini instruments that do not nounced as embryologists transformed into those of Jupiter’s satellites. Trafton also relate to Titan are not described. The last developmental biologists and adopted presented rather weak evidence that there chapter discusses what the mission will be many of the powerful new approaches might be a large amount of hydrogen. It like after arrival, and includes some ideas being used in molecular genetics and cell was suggested that the strange infrared on possible future missions. The book is biology. Yet morphology continues to be a appearance might be due to a warm surface, warmly recommended to the general reader key element of development – how could it maintained by the greenhouse effect. It and should be of considerable interest to be otherwise when the structural changes soon became evident, however, that part of the specialist. realized by an embryo are the bedrock the observed infrared emission is from a of the developmental process? Today, the warm stratosphere. It was also deduced that Donald M. Hunten

162 Endeavour Vol. 26(4) 2002