A hundred years ago the science of spectroscopy, though not yet christened, may be said to have attained its majority and to be just entering on its period of full adult development. It was born, of course, with Newton's explanation of the formation of the spectrum, and for many years thereafter little of importance was added to what he had discovered. It was not, in fact, until the nineteenth century that anything of outstanding importance occurred, and then, in 1802, Wollaston substituted a slit for the round hole through which Newton's sunlight passed into his prism, and thereby not only saw for the first time the dark lines in the solar spectrum but also took the first step towards the perfection of the spectroscope on which all later progress depended. The next step was taken by Fraunhofer who, in 1814, examined the spectrum through a telescope instead of letting it fall on a screen. The last essential improvement—the introduction of the collimator to make the light from the slit parallel before it entered the prism—was introduced in 1839 independently by Simms and Swan, so that before our period begins, the complete spectroscope existed, though it was not to be converted into a spectrograph, for photographing spectra, until much later.

Though quite short, the Edwardian era included a number of developments of critical importance for the interactions of science and technology. It saw the emergence of three really fundamental innovations in physics—relativity theory with its proof of the equivalence between mass and energy, quantum theory, and the disintegration of atomic nuclei. These have profoundly affected practical affairs as well as revolutionizing natural philosophy. Prominent amongst the many advances in applied science were the conquest of malaria, the mastery of aviation, the beginnings of electronics and wireless telegraphy, and the production of synthetic fertilizers by chemical industry. Successes and frustrations in British contributions to these striking changes in science and technology have an impact on history which is still being worked out.

I. Reputed shortcomings of Descartes as philosopher of science.

II ‘Knowledge’ in mathematics and in physics. The ‘ontological’ postulates of Descartes's philosophy and philosophy of physics.

III. The ‘foundations of dynamics’: ‘Newton's First Law of Motion’ and its status.

IV. Descartes's conception of ‘hypothesis’: the competing claims of the ideal of the a priori in physics and the conception of retroductive inference. (The status of the mechanistic world picture.)

V. Descartes's notion of ‘analysis’. The distinction between ‘procedure’ and ‘inference’. The notion of ‘induction’ and ‘understanding through models’: ‘Snell's Law of Refraction’.

Darwin only published one account of his provisional hypothesis of pangenesis, and that is to be found in chapter xxvii of his book The Variation of Animals and Plants under Domestication, the first edition of which is dated 1868. The absence of any earlier account in Darwin's works has led some to assume that he had recourse to this hypothesis only a short time before the published date of the book containing it, and on the basis of this assumption they have asserted that he produced it as a part of his defence of the theory of evolution against the criticisms made of it by the physicists Sir William Thomson, afterwards Lord Kelvin, and Fleeming Jenkin. But to make such an assertion is to ignore the fact that Darwin had already sent his manuscript of pangenesis to Huxley in the year 1865, two years before Fleeming Jenkin's article appeared and three years before Lord Kelvin openly attacked the evolutionary theory. The discovery of this manuscript of pangenesis has, therefore, some importance, for it should reveal Darwin's conception of pangenesis in 1865.

The history of the dyestuffs industry during the period 1775–1860 is interesting for three reasons. In the first place it was in connection with the manufacture of synthetic dyestuffs, begun in 1856, that the industrial research laboratory and the organization scientist first unmistakably appeared in the last decades of the nineteenth century. Secondly, there are the enigmas of W. H. Perkin, the man who discovered and manufactured the first coal-tar colours, but who retired somewhat abruptly from the industry in 1874: just after the synthesis of alizarine. Thirdly, the dyestuffs industry was in intimate association with the textile industries which had for a long time been subject to frequent radical scientific and technological innovation. Among the most important of these we may mention John Smeaton's classic paper of 1759 on the maximum work obtainable from a given fall of water: a problem important not only for the abstract science of mechanics, but also for the design of waterwheels—the main source of power for the early textile mills. (The waterwheel was not, during the eighteenth century, the epitome of the quaint and picturesque: it was in the van of scientific and technical progress.) Again, the textile industries were quick to employ the Watt rotative engine; previously a two cylinder Newcomen engine had been tried out. Bleaching powders, based on Scheele's discovery of chlorine and its properties, were rapidly adopted: in this context one cannot help contrasting the indifference of medical science to Davy's early suggestion of using nitrous oxide as an anaesthetic; or Faraday's comment in 1818 on the anaesthetic power of sulphuric ether. The textile industries saw, over this period, a rapid succession of new machines, the pace of invention being so hot that in 1832 Charles Babbage reported that machines became obsolete long before they wore out. A Salford cotton mill was the first industrial establishment to use gas lighting: James Thomson, calico printer, introduced gas lighting to the town of Clitheroe when he installed it in his works. And there were many other important technical and scientific innovations. It was to supply these industries, so well accustomed to change, that the synthetic coal-tar dyestuffs were introduced from 1856 onwards. It is interesting that, so far as we can see, the appearance of these synthetic dyestuffs was the last in the series of major innovations in the textiles and related industries: at least until recent times.