Trying to make a difference

The jury that awards the Aventis prize for science books is famous for wrong-footing the bookies. But next time you are in the betting shop, a fiver on The Cogwheel Brain for the 2001 shortlist is a solid investment. It has everything the judges like: a fascinating human story; a convincing evocation of a key era in history; explanations of ground-breaking science and technology; and a modern-day sting in the tail. And it is very well written.

Doron Swade's account of the early 19th-century era in which Charles Babbage developed his computers, the difference engine and the analytical engine, will make you grateful for your pocket calculator, let alone your PC.

Babbage's first idea was not to provide general-purpose computing as we understand it, although later on he did propose that the analytical engine might pay for itself by writing novels. Instead, the plan was to remove human error and effort from the production of tables by automating both their calculation and manual typesetting, during which further errors were introduced.

Navigation and astronomy were (and remain) major users of very precise calculations.The difference engine project was inspired by a mammoth proof-reading session in which Babbage and the astronomer John Herschel had to wade through hundreds of pages of tables produced for the new (now Royal) Astronomical Society. Many other astronomers appear as Babbage supporters and one, astronomer royal George Airy, as his main opponent.

For the tale of the difference engine is a tale of science politics and government funding. Airy was the manager and policy-maker for science, filling single-handedly a role that today employs a cast of thousands. Airy has had a bad press for advising the government against putting money into the Babbage engines. But as Swade sees it, he was right to argue that the same money spent on human "computers" would have produced much more data. And Swade points out that Airy softened his stance as the facts changed. He eventually supported the purchase of a Scheutz computing engine, designed by a Swedish team inspired by Babbage.

Swade makes use of the extensive Babbage archive, most of which is at his own institution, the Science Museum, to give us the interlocking tales of Babbage's amazing life, his career as an innovator, and the political and technological milieu in which they occurred. The Babbage we meet here is a polymath who invented the ophthalmoscope and wrote a book showing how life insurers scam the public. He railed against hereditary peerages, calling for life peers instead, and was a Liberal parliamentary candidate. And he attacked British neglect of science in a way that would seem familiar today. Few present-day publishers would risk the libels he seemed to get away with, at one point accusing Humphry Davy of pocketing the Royal Society's money.

However, all this was almost a family row in the circles Babbage moved in.Rich and well connected, he could, it seems, drop in for a chat with chancellors and prime ministers in the hunt for research funds, even if his interpersonal skills - he had a short fuse - meant that he made little of the opportunity.

Despite Babbage's advantages, the one thing everyone knows about his computers is that they never got built. Swade goes into the reasons for this failure in detail. One was the sheer difficulty of the task. There was no precedent for building a machine weighing many tons consisting entirely of precision components. Even standard-gauge screws and bolts were yet to be invented, an innovation deriving partly from the difference engine. But Swade shows that building the engine would have been difficult rather than impossible. The engineer Babbage worked with, Joseph Clement, may have been lining his pockets at the Treasury's expense but did seem able to produce the cogwheels and other components Babbage needed to the required tolerances. Instead, the engine seems to have run out of time, money and friends. It had too few influential allies, despite the government's appointing Herschel, a believer and Babbage's oldest friend, more than once as an adviser on the scheme's viability.

But Swade does find that another Babbage myth, that he got bored with the difference engine when he became excited by its successor, the analytical engine, is true. The analytical engine was an immense intellectual feat, and included innovations such as stored programs, iteration and logical branching. It would have been a computer rather than a calculator as the difference engine was, and it is no surprise that Babbage found it all-engrossing once he grasped the horizons it could open up.

The Cogwheel Brain is a substantial contribution to our knowledge of Babbage and the early history of computing. But almost as gripping as its 19th-century tale is the 20th-century one that makes up the last quarter of the book. Here Swade switches to the first person as he leads the project to build the difference engine Babbage never saw, on the basis of the rich holdings of drawings and parts at the Science Museum and elsewhere. Now the story is not one of Wellington, Peel and Airy but of Thatcher, IBM and ICL. Swade and his colleagues built the engine in a climate of budget cuts and the need for corporate sponsorship, and had to finish it by Boxing Day 1991, the bicentenary of Babbage's birth. IBM, one possible sponsor, seems to have taken a crude public-relations view of the opportunity, which in the end was funded by a consortium of UK information technology firms, assembled by the government during the British IT fever of the 1980s.

Swade concludes that, with some minor exceptions, Babbage's work did not influence later developments in computing. One of his biggest breakthroughs, the separation of memory from processing - the mill and the store, as he called them - was reinvented by John von Neumann over a century after Babbage had the idea.

But Swade's difference engine project was a prime beneficiary of the modern computer industry's sense of history (or, to the cynic, its wish to buy itself a past), manifested in the high prices paid for early calculators and mathematical documents. The Science Museum machine now has the printer Babbage intended - not a peripheral as we know them, but an integral part of the machine - after a $1.2 million gift from Nathan Myhrvold, Microsoft millionaire. The 4,000-piece printer was beyond the budget of the original project and with its addition the engine is complete. It is an astounding exhibit, which has a worthy companion in this book.

Martin Ince is deputy editor, The THES .