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history may get the impression that objectivescientific factors did not have much influenceon the success of physics, although that is notthe author’s position. While acknowledgingthe importance of mathematics in the devel-opment of theoretical physics, he provides fewequations and no discussion of any mathemat-ical concepts or techniques; this may pleasesome readers but it fails to convey an under-standing of what theoretical physicists such asHermann von Helmholtz, James Clerk Maxwelland Augustin-Jean Fresnel were actually doing.

Why did physics rather than chemistrybecome the leading science by 1900? Theauthor’s answer is fourfold. First, physics wascredited with establishing the law of energyconservation, the most important discovery in nineteenth-century physical science. Thislaw governed all the physical and biologicalsciences, and was even believed to explain whywomen should not do scientific research.Some nineteenth-century scientists arguedthat “only so much energy could be containedin a woman’s body. Its proper purpose was tobe directed towards childbirth and nurturing.”

Second, Morus believes that the math-ematical aspects of physics “made laboratorywork respectable for the sons of gentlemen”,thereby overcoming class prejudice against themanual labour needed to do experimental science. Third, “its connexions with the worldof telegraph cables, electric power, and factoryengines made it a practical occupation for thesons of trade”.

The final reason that Morus gives for therise of physics is that it gained favourable

notice from public demonstrations andexhibits, especially of electrical phenomena,and from applications that benefited industry,government and citizens. For those scientistsand others fascinated by “mysterious fluidsand forces” at the end of the nineteenth cen-tury, he says, the electromagnetic-wave exper-iments of Heinrich Hertz not only confirmedthe remarkable prediction from Maxwell’sequations of their existence and properties, but also “demonstrated graphically the physicists’power to manipulate nature, to make thingshappen as if by magic”.

Going back up the causal chain, we learnthat the University of Cambridge began tostress advanced mathematics because, at thebeginning of the nineteenth century, that was the only subject to be tested by writtenexaminations leading to public honours.Attaining such honours was the best way toenter a career in government service in theexpanding British Empire. Success in themathematical tripos examination was sup-posed to demonstrate the moral and mentalcharacteristics needed for such service. Prep-aration for this very competitive examinationprovided excellent training for research in theoretical physics.

Then, around 1870, despite strong univer-sity opposition, a laboratory for experimentalwork was established. This was only possiblebecause William Cavendish, Duke of Devon-shire, who had himself attained high honoursin mathematics, was chancellor of the univer-sity and paid for the laboratory himself. TheCavendish Laboratory got off to an excellentstart with the efforts of Maxwell, its first director, and so the University of Cambridgebecame a world leader in both theoretical andexperimental physics. A similar story, com-bining social and personal factors, can be toldabout the rise of physics in Germany.

It is impossible to cover all the importantaspects of nineteenth-century physics in a textof fewer than 300 pages. However, a seriousomission from Why Physics Became King is theestablishment of the existence and quantita-tive properties of atoms. The contributions ofAvogadro, Loschmidt, Perrin and others areignored. Although in the nineteenth centurythe atom may have been more important tochemistry than to physics, it was thanks tophysical theories (especially the kinetic theoryof gases) that the speeds, masses and sizes ofatoms could be determined. This transformeda philosophical speculation into a legitimatescientific concept and expanded the kingdomof physics into fertile new territory. ■

Stephen G. Brush is professor of the history ofscience in the Department of History andInstitute for Physical Science and Technology,University of Maryland, College Park, Maryland 20742, USA.

Laying down the lawsWhen Physics Became Kingby Iwan Rhys MorusUniversity of Chicago Press: 2005. 288 pp.$60, £42 (hbk); $25, £17.50 (pbk)

Stephen G. BrushWhen did physics become king? And what isits kingdom?

According to Iwan Rhys Morus, a lecturer in history at the University of Wales, it wasduring the nineteenth century that physicsbecame the most powerful and prestigious science in the United Kingdom and Germany.

That does not necessarily mean that other sciences bowed down to physics — the onlyother sciences he mentions are chemistry andastronomy, both of which had been dominantin the early part of the century. Apparently,chemistry failed to keep up with physics, whileastronomy became more and more dependenton physical instruments and theories.

This is a story about the ascendance ofphysics as viewed by the public and, moreimportantly, by government and industry. AsMorus puts it, physics became “the ultimateauthority in nature”. It is a fascinating story,well told and mostly based on the latestresearch by professional historians of science.But the approach is “unashamedly cultural”, orrather, social: high culture appears only in achapter on romantic nature philosophy.

Morus stresses the role of institutions suchas universities, journals and public exhibitions,alongside events that depended on the actionsof individuals. Readers who don’t have somebackground knowledge of physics and its

EXHIBITION

Snow businessWilson ‘Snowflake’ Bentley hada lifelong obsession with theintricate hexagonal symmetryof snowflakes. He producedmore than 5,000 photo-micrographs, compiled in his 1931 landmark book Snow Crystals, and in otherpublications.

An unseasonal exhibition atthe New York Academy ofSciences, ‘One of a Kind’, pairsBentley’s images with works on the same theme bycontemporary artists,including Daniele Imperiale-Warner, whose egg tempera on parchment painting,Untitled, is shown here.

The exhibition runs until 31 August. A.P.

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