Reviews 353

Jimena Canales, A Tenth of a Second: A His-tory (Chicago: University of Chicago Press,2009), 288 pp.

This scintillating book recounts a nearly cen-tury-long obsession with the ‘sacred 0.1 sec-onds’, from around 1850 to the eve of theSecond World War. The problem had its deeporigins in Descartes’ assertion that reactionand stimulus occurred ‘at the same time’. Butany ambition to challenge Cartesian mind-bodydualisms at their interface in the nervous sys-tem remained feckless until the 1840s, whenseveral different kinds of measuring devices -galvanometers and graphical recording instru-ments - made it possible to demonstrate a lagtime between stimulus and response. A scien-tific consensus formed around the time requiredby an intelligent person to perceive and to will:about one tenth of a second.

From about 1850 the measurement of thetenth of a second became a key dimension ofscientific problems across the disciplines. Astro-nomical observations hinged critically on thereaction-times of observers, especially in the‘eye and ear’ methods of determining time andlongitude. After 1850, reaction times and per-sonal equations became staples of any obser-vational science that required physiologicalintermediaries. Experimental psychology madereaction-times the centerpiece of its disciplinaryidentity, with the experimental system of stim-ulus, a subject, and a recording device, and atleast a tenth of a second elapsed between begin-ning and end of the operations.

Canales goes well beyond these familiar sto-ries, however, showing just how fundamen-tal tenth of second measurement was for bothpractical metrological problems in physics andphilosophical problems of many kinds. Sheshows, for example, how debates about theobservational measurements of the transit ofVenus across the sun in 1874 became embroiledin debates over chronophotography and thepersistence of retinal impressions, which, as ithappened, sustained a perception of movementwhen images appeared at intervals of about a

© 2010 John Wiley & Sons A/S

354 Reviews

tenth of a second. Canales ties these debates tothe technical development of cinematography,as well as to broad-gauge philosophical discus-sions about the perception of moving images.

Still more remarkable were the effects ofthese debates on modern physics. Speed-of-light experiments in physics gained importancebecause of tenth-of-a-second errors in astron-omy. A new definition of the meter (in terms oflight waves) gained currency because of tenth-of-a-second errors that haunted previous deter-minations of this standard. Interferometry, thepinnacle of precision science, was developed toovercome errors at this magnitude. It was, ofcourse, Albert Michelson’s inferometric speedof light experiments that provided a criticaltouchstone for Einstein’s theory of relativity.Canales examines debates over relativity fromthe vantage point of this history, opening someremarkable new vistas on well-trodden histori-cal terrain.

To tell her history of brief time Canales hashad to untangle some rather densely woven his-toriography that had long framed the historyof reaction times and the personal equation.The ‘standard account’ emphasized the his-tory of astronomy and experimental psychol-ogy, and more tendentiously, the movement ofprecision measurement from the physical sci-ences to the human sciences. Canales dispelsthis narrative by exploring a range of nationaland disciplinary sites where early reaction timeresearch was pursued. Besides measurements ofthe speed of thought there were experiments onacoustics, optics, ballistics, astronomy, photom-etry and measurements of the speed of lightthat dealt with physiological intermediaries.Canales shows how the narrative of the ‘stan-dard account’ was propagated by the Frenchphilosopher and psychologist Theodule Ribot asa local polemic on behalf of burgeoning Frenchexperimental psychology. Ribot described apost-Kantian era invented in rival Germany, inwhich quantification was extended to includeeven the psyche, with personal equations reveal-ing individual traits of personality, nervousconstitution, health, education and intelligence.

This narrative was repackaged for the his-tory of science by the Harvard psychologistEdward G. Boring, who used it to illustratethe general march of scientific advance throughquantification and measurement. Thomas Kuhnchallenged Boring’s account, arguing that mea-surement was not progressive but relativeto a theory-driven scientific paradigm. SimonSchaffer extended Kuhn’s critique of Boringinto a social, cultural, and labor history of mea-surement, with the personal equation as a primeexample. Measurement, Schaffer argued, shouldbe the science historians’ method for unlockingthe problem of modernity.

Canales’ history of the tenth of a secondmakes a major contribution to this project.She shows how Baudelaire’s oft-cited notion ofmodernity - the ‘ephemeral, fleeting, the con-tingent’, which nevertheless recaptured ‘some-thing eternal’- echoed the scientists’ quest tofind a stable natural constant in a dynamic andevanescent world. Canales shows how literary-philosophical formulation also expressed thecentral problem of integrating humans inscience-based industrial and media systems(e.g. steam, rail, telegraphy, telephony) whichrequired connections between material compo-nents and eyes, ears, hands and brains. ‘We alllive on a tenth of a second world’, wrote anassistant to Thomas Edison in the 1920’s.

Another key concern of the book is the rangeof new philosophies that emerged from theinterfaces of the modernist hybrid systems. Ifyou have ever fretted over why the canonicaltraditions of philosophy seem to disappear after1850 this book may provide relief. Modernconceptions of the tenth of a second are cen-tral to the thought of Henri Bergson, WilliamJames, and others concerned with the bound-aries of modern life between reality and illusion,action and passivity, psychology and physi-ology, human and non-human. An illuminat-ing chapter considers public debates betweenBergson and Einstein over the effects of relativ-ity on time and simultaneity, a quarrel of philo-sophical and political consequence that hingedespecially of the interpretation of reaction timeexperiments. More broadly, the widespread

© 2010 John Wiley & Sons A/S

Reviews 355

popular uses of the term ‘personal equation’,captured a new sense of personal identity inthe technical and statistical matrix altogetherdifferent from older notions of ontological indi-viduality. A range of similar philosophical dis-cussions, mostly ignored today, arose that wentbeyond traditional categories of ‘man’, ‘thing’,‘science’, ‘society’, and ‘politics’. Still, Canalesprobably falls a little short of her frequentlystated aim to ‘search for alternatives’ to themodernity she has uncovered. One gets a fleet-ing impression that Canales has come to believein the ontological existence of the tenth of sec-ond whose contingent history she has written.Like its subject, Canales’ book is relatively briefand, at times, fugitive. But it frames a vastsweep of modern history. It should - at least fora moment - set a new historiographic standardfor many to follow.

Robert BrainUniversity of British Colombia, Vancoover

© 2010 John Wiley & Sons A/S