It is reasonable to suppose that science, as we now know it, had its beginnings about the time of Elizabeth I. As such, it can therefore claim to have generated a history. The history of science has now become a very fashionable topic of study, especially of academic study, resulting in the creation of university departments and professors of the subject both in Europe and the United States.

The first of these two books, The Values of Precision, is a series of 13 essays, three of which are summary essays by the editor. All of the authors are historians, being either professors or lecturers in university departments which are concerned with the history of science.

The second book, Trust in Numbers is a full-length treatise by Theodore Porter, one of the 11 essayists in the first book.

Any nonspecialist reader is strongly advised to begin with the essays, for each is, of necessity, of limited scope and generally directed to the history of a relatively short period or to a specific topic, making it very readable.

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For example Chapter Six, by Simon Schaffer, a specialist reader from Cambridge University, is all about Maxwell's discovery of electromagnetic waves and the fact that their velocity, as predicted from the relationship between the electrostatic and electromagnetic units of electrical quantities was the same as that of the velocity of light. Maxwell was, of course, not believed, and the chapter continues by describing how more and more accurate measurements of electrical resistance on the one hand and the velocity of light on the other, were made until the discrepancy was of the order of 1 per cent. This chapter is extremely easy to read and will be of considerable interest to engineers and others whose daily work makes use of scientific discovery.

Chapter Ten is concerned with the history of Victorian technologists such as Ayrton and Perry who strove to develop the classical instruments for measuring electric current, such as the tangent galvanometer and Ampere's current balance (essentially fragile apparatus belonging to the research laboratory of that time) into commercial ammeters and voltmeters of robust construction, without losing the accuracy of their predecessors.

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The opening chapters tell the story of the rise of the metric system, a topic of particular interest to most of us at the present time, when legislation regarding how we shall measure our purchased goods in future is about to change our lives in the United Kingdom (but not, of course, in France).

According to legend Napoleon decided that a metre should be one ten-millionth part of the distance from the pole to the equator in a great circle, but it was not quite as simple as that.

The author of Chapter Two states: "This then is the story of how a national language - the metric system - was deliberately crafted to break the hold of the Old Regime's political economy and serve as the universal idiom of the modern mechanism of exchange."

Other chapters give the views on the subject of a physiologist, a chemist and a mechanical engineer who seems primarily to be interested in steam engines.

The least interesting chapter, unfortunately, is that by Theodore Porter. Here is an academic purist who seeks to cover the whole subject in all its facets, and having researched it very thoroughly, as his profession demands, has failed to write it up in a language that is accessible and interesting to the nonspecialist.

I confess to having read his book first and to have decided that if this was typical of the way the history of science was being taught, then it is boring, pretentious and full of generalisations that are about as accurate as the notion that England is a nation of shopkeepers and is therefore not really worth the trouble of reading.

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Ido not say that Porter's book is totally boring. It is just that I kept finding myself counting the pages that still had to be read, and it came as a refreshing change to read the essays of the other book.

Whereas it is not obvious from reading almost any of the short essays whether the writer is a scientist, engineer or historian, it is quite obvious that Porter is a historian, and a dedicated one. Historians tend to accumulate a sequence of facts, then invent a reason for them to have occurred like that. This of course, does not necessarily mean that it is the right reason.

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For example, in his preface he says, "I argue that the transition from expert judgement to explicit decision criteria did not grow out of the attempts of powerful insiders to make better decisions, but rather emerged as a strategy of impersonality in response to their exposure to pressures from outside." I am sure it was not like that. From the earliest times it was all a question of "I've got more sheep than you have!" He is also guilty of interpreting writings in disregard of what the authors of those writings intended. This is a favourite occupation of vicars from pulpits on Sundays in relation to the Bible. How else would there be enough material for thousands of new sermons every Sunday? One feels that the author of this book could now go on to write other books such as, "the part estimation played in the evolution of science", "the development of science in terms of olfactory response" and many others, until it becomes a way of life.

Again in the preface, he includes the almost incredible sentence, "The interpenetration of science and technology, I now concede, is unmistakable, especially in the current century." Porter reminds me of the character in Moliere who, in his riper years, discovered that "all his life he had been speaking prose".

Worst of all, perhaps, he confronts his potential reader on page one, line one of the text proper, with this: "Objectivity arouses the passions as few other words can." Someone should tell him to try sex, gay, the EEC and the Cup Final on people in the nonacademic world.

Compare this with the honest, down-to-earth reason for writing on the subject of precision given by Schaffer at the start of his chapter of The Values of Precision: "Precision badly needs a cultural history."

Here is a man who has a story to write and a clear message for the reader. But if one becomes so deeply engrossed in library research in its own right and loses sight of the real world, one is liable to do as Porter does and produce gems of wisdom such as: "Engineers are often required by their profession to practise economics."

This must surely be good news for all of us.

Eric Laithwaite is emeritus professor of engineering, Imperial College, London, and visiting professor, University of Sussex.

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