Through the years there have been subtle changes in the evaluations of the work of Tycho Brahe. As one examines the tracts dealing with novae and comets in which reference is made to the nova of 1572 or the comet of 1577, it becomes quite evident that in different parts of Europe and in the Near East and at different periods of time and among men of different religious convictions different values were placed on his work. The extent of his influence should be distinguished from the measure of his achievements. Moreover, his importance cannot be completely separated from that of Kepler and the horde of other writers who furnished more than a mere background for the display of Tycho's brilliance. Here, as always, there is the danger of assigning to one man innovations that were, so to speak, in the air.

The years between 1660 and 1800 were important ones in the study of light. For most of the period the work, especially in this country, was largely dominated by the theories advanced by Newton; unfortunately the protagonists of these theories were much more rigid in their approach than was Newton himself. There was, in effect, almost a century of ‘rear-guard actions’ to maintain the corpuscular theory at all costs.

Fortunately, the advance of geometrical optics and the design of optical instruments was not retarded to a very great degree by this partisan approach. The workers in these fields were not, as a rule, too involved in speculation, and worked largely empirically.

Some of the modifications to the original corpuscular theory are interesting. Attempts were made to explain, with varying degrees of success, total internal reflection, dispersion, interference effects, diffraction and phosphorescence. Considerable speculation about the velocity of light occurred in connection with these topics. At the same time, wave theories never completely died out and, although they were not developed until the early part of the nineteenth century, their influence was felt even in this country.

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.

The Geological Society of London was the first learned society to be devoted solely to geology, and its members were responsible for much of the spectacular progress of the science in the nineteenth century. Its distinctive character as a centre of geological discussion and research was established within the first five years from its foundation in 1807. During this period its activities were directed, and its policies largely shaped, by its President, George Bellas Greenough, on whose unpublished papers this account is chiefly based.

The Society began as a small scientific dining club in London, but it developed rapidly into a learned society with a nation-wide membership. It became so independent in outlook and so active in research that it was felt to threaten the esteem of the Royal Society; and little more than a year after its foundation it clashed with the Royal Society (and especially with its President Sir Joseph Banks) so violently that its continued existence was for a time uncertain.

Its development into a large independent society was the outcome of its ‘Baconian’ view of the importance of collecting geological facts as a surer basis for geological theories. For this purpose it initiated an ambitious scheme for co-operative research, which would unite the efforts of ‘philosophers’ with those of ‘practical men’. Only personal reasons seem to have kept the most prominent of the practical men—William Smith—from co-operating with the Society.

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.

George Greenough (1778–1856) was one of the influential group of early nineteenth-century English geologists who rejected both Hutton's and Werner's attempts to propound all-embracing geological theories, and followed a deliberately empirical approach. He travelled through Scotland in 1805, studying geological phenomena in the light of both the Plutonist and the Neptunist theories, and generally concluded that neither was entirely satisfactory as an explanation of the observable facts. He was also the first to suggest that the ‘Parallel Roads’ of Glen Roy were the successive beach-levels of a former lake: this theory was later attacked by Darwin but ultimately vindicated by Agassiz's glacial theory. The more important geological passages from Greenough's MS. journal of the tour are reproduced and discussed in this paper. They illustrate some of the scientific problems that were involved in accepting either Hutton's or Werner's theory entire.

The University of Leyden was founded in 1575 as the reward of the city's endurance of the Spanish siege in 1574. Its influence on botany in the seventeenth and eighteenth centuries is part of its far-reaching influence during this period on medicine, to which botany was then ancillary. In this it was the successor of Montpellier and Padua. The first university founded after the Reformation to practise and maintain religious tolerance towards its students, Leyden became the great international university of Europe, drawing students from Scandinavia, Germany, Switzerland and France, from all parts of the British Isles and the British American colonies (roughly 4,000 English-speaking students between 1600 and 1750) and even from Barbados, Jamaica and Constantinople. It offered facilities for higher education then denied, for example, to dissenters in England or else not available, as in Scandinavia. Owing to this religious tolerance in an age of intolerance and also to the personal eminence of a succession of professors, its influence spread widely. Directly and indirectly, Leyden made its greatest contribution to botany and medicine through the work and personality of Herman Boerhaave (1668–1738) and led to the founding or restoration of botanic gardens at Edinburgh, Göttingen, Uppsala and Vienna. Beginning with Clusius, its influence upon botany may be traced through Hermann and Boerhaave to Haller, Linnaeus, Lettsom and others. No other university has a more sustained and continuous record of service to botany and medicine during these two centuries than Leyden. This paper also touches upon the history of other universities.

Scurvy is now almost a forgotten disease, but it would be difficult to exaggerate its importance in the history of a maritime nation such as our own. To the historian of medical science it is equally interesting, because the various and extraordinary variety of theories concerning it reflect in themselves the intellectual climate of the past. By their repeated refusal to accept the conclusions of an experimental method, by their pedantic reliance on a priori reasoning or antiquated prejudices, the medical authorities of all countries delayed the conquest of this terrible disease long after a cure had been established by men who had practical experience of it. If anyone imagines that even in scientific knowledge progress is inevitable, let him remember that scurvy continued to be the curse of the sea and the hardship of explorers so recent as Scott and Shackleton a hundred years after it had been eliminated in the fleets of Nelson's day.

Three questions of major historical interest may be asked concerning the neglect and the rediscovery of Mendel's work.

1. Why was it so little noticed between its publication in 1866 and its rediscovery in 1900?

2. What factors determined its rediscovery?

3. What factors favoured the rapid growth of Mendelian genetics?

It is with the second and third of these questions that this paper is concerned.

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 rapid growth of seventeenth-century science is said to have been facilitated from four main outside channels: the arts, medicine, economic life and war, each of them influencing, to some extent, the important scientific achievements of the latter half of the century. The bitter campaigns of the English Civil War stimulated a rough and ready empiricism, as military necessity brought forth increasing advances in engineering, navigation, cartography, medicine and surgery. And the impetus to inventive genius provided by long experience in the art of war is well exemplified in the career of the Royalist Commander, Prince Rupert of the Rhine. After nearly forty years of waging war on land and sea, Prince Rupert, German-English nephew of Charles I, spent his retirement in busy experiment; and many of his inventions, though based on his knowledge of weapons, were later adapted for peaceful purposes.

Simon Bredon was one of a remarkable group of scientists who brought fame to Oxford by their achievements in the sphere of natural science, particularly in astronomy. Though his interests lay chiefly in the field of medicine, as indicated by the large collection of books on this subject which he bequeathed to his friends, he was also a mathematician and astronomer.

The manuscripts of his works, still preserved at Oxford, Cambridge and the British Museum, which include an arithmetic, a commentary on the Almagest, a theory of the planets and astronomical calculations, have never been properly examined and some kind of preliminary investigation seems necessary before his true position among the Merton school of scientists can be assessed.

The following essay is adapted from one with the same title read to the British Society for the History of Science on 20 October 1958—the anniversary, by a striking coincidence, of the birth of W. H. Young (1863–1942). To his memory I dedicated the talk, and now rededicate its publication, not only because I am his daughter and of all that means, but because he invented a method, the method of monotone sequences, which shows the powerfulness of inequalities as a mathematical tool supremely.

Taking Isaac Newton at his own word, historians have long agreed that the decade of the 1660s, when Newton was a young man in his twenties, was the critical period in his scientific career. In the years 1665 and 1666, he has told us, he hit on the ideas of cosmic gravitation, the composition of white light, and the fluxional calculus. The elaboration of these basic ideas constituted his scientific achievement. Nevertheless, the decade of the 1660s has remained a virtual blank in our knowledge of Newton. It need not remain so always. His papers contain a wealth of manuscripts from his undergraduate years and the period immediately following. The first volume of his mathematical papers, which will soon be published, will demonstrate how extensive the information on his early mathematical development is. The development of his non-mathematical studies, especially of what I shall call his scientific studies to distinguish them from the mathematical, can be followed as well—in his reading notes, in his notebooks, above all in the passage in his philosophical notebook labelled Quaestiones quaedam Philosophicae. In this passage we see emerging into consciousness for the first time the questions on which Newton's philosophy of nature was built.

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.

Some of the early superstitious beliefs concerning communication by means of magnets are mentioned.

Some of the suggested ‘static telegraphs’ are described, together with the reasons for their failure. An account is given of the rise of the use of the electric current in the telegraph by continental workers early in the nineteenth century, and the manner in which this method became known in England. The work of Cooke and Wheatstone is briefly outlined, and the assistance given to the English workers by Joseph Henry.

The development of the American telegraph in the hands of Morse is reviewed, and the similarity of the difficulties experienced by Morse and by Cooke. The origin of the relay is examined.

The commercial success of the telegraph was largely due to the several needs it fulfilled, and the uses of the telegraph are enumerated.

Submarine telegraphs and especially the Atlantic telegraph are described together with the mechanical and electrical difficulties associated with long distance telegraphy through cables. In this connection the work of William Thomson is very briefly reviewed.

The growth of the telephone out of the telegraph at the hands of Bell in America is described, and is shown to be achieved as a result of the synthesis of Bell's knowledge of physiology and of electricity. The paper concludes with a statement of the commercial success of Bell's telephone.

A eudiometer formerly believed to have belonged to Henry Cavendish was probably made after his death. It may have belonged to John Dalton.