Popular Science Monthly/Volume 52/December 1897/Sketch of Joseph Prestwich
SIR JOSEPH PRESTWICH.
| SKETCH OF JOSEPH PRESTWICH. |
SIR JOSEPH PRESTWICH was, at the time of his death, the oldest of British geologists. While his scientific honors were numerous, the formal recognition by his Government of the value of his work, much of which had redounded greatly to the material advantage of England was tardy. It came to him in the form of a complimentary knighthood only on the New Year's day before his death in the following June, when he was not able, on account of feeble health, to accept it in person from her Majesty. Till 1872 Dr. Prestwich curiously combined the two occupations of wine merchant and geologist. His business took him frequently to France, and while there he sought and improved the opportunities he found to make geological studies of the districts he visited; and it is told of him that his friends used to like to go geologizing with him on the other side of the Channel, "as his walks generally ended in the pleasant chateau of some vine-grower."
Joseph Prestwich was born in Clapham, England, March 12, 1812, and died in Shoreham, Kent, June 23, 1896. He was taught at London and Paris, and in Dr. Valpy's Grammar School in Reading, and afterward studied at University College, Gower Street, London, where he gave special attention to chemistry and natural philosophy under Prof. Edward Turner and Dr. Dionysius Lardner. There also his attention was first drawn to geology and mineralogy, which were among the subjects in Turner's course. After he went into business he continued to devote all the leisure he could command to the study of geology, first as a means of relaxation and afterward on account of the scientific interest he took in it.
He began publishing scientific papers in 1835, when he was about twenty-three years old, his first, on the Ichthyolites of Gamrie, Banffshire, Scotland, having been printed in the Transactions of the Geological Society of that year, and some of his earlier papers on the Coalbrookdale Coal Field being of the same period. Other papers followed in the Quarterly Journal of the Geographical Society on Structure and Organic Remains of the Tertiary Beds of the London and Hampshire Basin, in which many now fully accepted facts of geological sequence and relations were first established. In these researches he paid special attention to the lithological changes of the strata and to the fossils. In consideration of this earlier work he was awarded the Wollaston medal by the Geological Society.
Having acquired some familiarity with the geology of France by his former residence as a student and his frequent business there, Mr. Prestwich, in the course of the studies which resulted in the rearrangement of the Tertiary formations, carried his explorations across the Channel to the corresponding formations of France and Belgium, for the purpose of determining the correlation of the strata. In the course of these investigations, at the suggestion of Dr. Hugh Falconer, and in company with Sir John Evans, he examined the valley gravels containing flint implements—works of man—associated with the remains of extinct animals, the discovery of which in the valley of the Somme had been announced by M. Boucher de Perthes without attracting special attention. The finds made here could be compared with the somewhat similar discoveries made in England in Kent's Cavern by McEnery and in Brixham Cave in 1858. All these evidences of man's antiquity, together with others subsequently found in England, were studied by Prestwich and Sir John Evans, with the result of fully establishing the contemporaneous existence of man with other Pleistocene mammals. The question of the duration of man's existence upon the earth thus became a subject of lively discussion, which still continues. The theory of man's extreme antiquity, as indicated by these remains, which Mr. Prestwich was inclined to embrace at the time, and which he was among the first to promulgate in England afterward, underwent a process of modification in his mind, and he was disposed in his later works to reduce considerably the estimates he made then. In recognition of his work as one of the pioneers in establishing the geological antiquity of man, the Royal Society in 1865 awarded him the Royal medal.
As Dr. Prestwich grew older he paid more and more attention to economic geology, and finally became one of the most eminent authorities in that branch. His earlier studies on Coalbrookdale and the Tertiary strata seem, in the light of after developments, to have been preparatory, though unconsciously so, for such a career. A lecture on the geology of Clapham—The Ground Beneath Us—delivered about forty years ago to a local society, and his publication on the water-bearing strata of the country around London, were in that direction. The former work "has stood the tests of time remarkably well," and the latter, first published in 1851, has become a standard, and has lately been reissued with appendices. He was engaged upon the Royal Commission on Metropolitan Water Supply and upon the Royal Coal Commission, to the reports of which he contributed valuable papers, one of them embodying the conclusion that the coal fields under the Secondary rocks of the south and southeast of England might extend from Somersetshire to the neighborhood of Folkestone, which has been confirmed by borings at Dover.
Dr. Prestwich retired from business in 1872, and in 1874 became professor of geology at Oxford. He continued his researches with his accustomed activity, and enriched the literature of geology from year to year with numerous valuable and original contributions, in the form of papers and addresses to learned societies, in connection with which his name constantly appears, and of books which are indispensable to the thorough student of the science.
Dr. Prestwich's annual address as president of the Geological Society in 1872 gives an admirable, statement of the purposes of geological research with reference to the advent of man, and further on of its practical applications to the questions of water supply and coal. Among the theoretical problems that were then occupying the attention of geologists of all nations, the speaker said, were the phenomena connected with the prevalence of great and exceptional cold immediately preceding our time, the first dim appearance of man, his association with a race of great extinct mammalia belonging to a cold climate, the persistent zoölogical characteristics of man as contrasted with the variable animal types presented in geological time, the search for connecting links, and the measure of man's antiquity. Allied to these were the great questions relating to the forms of the continents—the elevation of the land, the origin of valleys and plains, and all that prepared the globe for the advent of man. Further, geology dealt with the requirements of civilized man, "showing him the best way of providing for many of his wants, and guiding him in the search for much that is necessary for his welfare. The questions of water supply, of building materials, of metalliferous veins, of iron and coal supply, and of surface soils all come under this head and constitute a scarcely less important although a more special branch of our science than the paleontological questions connected with the life of past periods, or than the great theoretical problems relating to physical and cosmical phenomena." Proceeding to consider the geological questions connected with water supply, the author suggested that the site of a spring or the presence of a stream determined probably the first settlements of savage man; and his civilized descendants, until the last few years, equally depended upon like conditions. These conditions were connected with the rainfall and with the distribution of the permeable and impermeable strata forming the surface of the country. Under ordinary circumstances few large towns had arisen except where a localized water supply was easily accessible, where the catchment basin controlling the volume of the rivers was large, and where permeable strata prevailed. Thus it was with London, and the extension of that city had worked along in those directions where water was got with the best facility. The second part of the address related to the work of the Royal Commission to examine into the coal fields and the coal supply, under which Dr. Prestwich was charged with the study of the districts covered by the later Secondary and the Tertiary strata, with the special object of inquiring "into the probability of finding coal under the Permian, new red sandstone, and other incumbent strata. The discussion of this subject implied a survey of the coal fields of England, France, and Belgium, and the possible connection through strata underlying the formations named. Several regions were indicated where trials for coal might be made, which it was admitted, however, might be attended with considerable uncertainty. But whether successful or not as to coal, such trials near London could hardly fail of some important results; for it was "possible that the lower greensands would at some spots be reached, so that the inestimable additional benefit of a large and steady supply of pure water might also be obtained, and with proper care to prevent interference might be maintained for all time."
Commending Dr. Prestwich's investigation of the sources of the water supply of London, and the presentation of the results in his book on that subject—"a masterpiece of minute observation and close and accurate reasoning"—Prof. J. W. Judd observed that the geologist could point to the work "with pardonable pride as affording convincing proof that his science has now acquired a character for exactness analogous to that which is justly regarded as the crowning attribute of astronomy." His predictions as to the finding of coal underneath the Secondary rocks across the kingdom were likewise justified in the results of borings made near Dover.
An important practical application of Dr. Prestwich's investigations of the geology of the English Channel, not anticipated when they were begun, was illustrated in his report on the subject to the Institution of Civil Engineers, presented in December, 1874. This report was described by Nature as being a most excellent example of the indispensability of thorough scientific research as a basis for the useful arts, and of the way in which the highest practical results unwittingly follow from such investigations—made in abstract inquiry, the only end of which was thorough knowledge of the subject in all its scientific aspects and relations. This study of the strata underlying the Channel—an almost perfect example of close and careful reasoning on physical facts—was now brought forward to enlighten the projectors of a tunnel between England and France as to the nature of the material on which they would have to work; but Dr. Prestwich had distinctly stated that the various formations were considered "irrespective of their relative merits in any other than a geological point of view." His plan had been to discuss carefully all the strata underlying the Channel, from the London clay down to the Palæozoic series, and deduce his conclusions as to the fitness of each formation for being pierced by a tunnel. The investigations on which the paper was founded were mostly undertaken from no practical point of view and before a Channel tunnel was thought of.
Dr. Prestwich's inaugural address as professor at the University of Oxford, in January, 1895, was on the Past and Future Work of Geology. We had no reason to suppose, he held, that during the greater part of the geological periods life in one form or another was not as prolific, or nearly so, in the British areas as at the present day. We might thus form some conception of how little relatively, though much really, we had so far discovered, and of how much yet remained to be done before we could re-establish the lands and seas of each successive period, with their full and significant populations. This we could not hope ever to succeed in accomplishing fully, for decay had been too quick and the rock entombment too much out of our reach ever to yield up all the varieties of past life; but, although the limits of the horizon might never be reached, the field could be vastly extended; each segment of that semicircle might be prolonged we knew not how far; and it was in this extension—this filling up the blanks in the life existing in each particular period—that one great work of the future lay. The speaker then considered two objections which had been urged against what had been called the cataclysmic theory in opposition to the uniformitarian theory—both terms characterized as objectionable in their exaggeration: one, that we required forces other than those which we see in operation; and the other that it was unnecessarily sought in that theory to do by violent means what could be equally well effected by time. The question raised in this theory is not, however, as to the nature of the force, but as to its energy; not a question of necessity one way or another, but of interpretation, of dynamics and not of time; and we can not attempt the introduction of time in explanations of problems the real difficulties of which were thereby more often passed over than solved. Time might and must be used as without limits; there was no reason why any attempt should be made either to extend or control it; but while there was no need for frugality, there was no reason in prodigality. After all, it would be found that, whichever theory was adopted, the need would not be very difficult. The mountain range, for the gradual elevation of which one would ask one hundred thousand years, the other might require for its more sudden elevation a force which had taken the same number of years to accumulate its energies.
Discussing in the Geological Society in 1889 the distribution and probable age of some palæolithic flint implements, Professor Prestwich maintained that the removal of the material observed indicated the existence of agents of greater force than those operating under the present river régime. This closed up the time required for the completion of the great physical phenomena, though the author's inquiry tended to carry us further back geologically than was usually admitted.
In a paper read at the British Association in 1881 on the causes of volcanic action, Professor Prestwich presented objections to the generally accepted theory of Scrope that eruptions are a phenomenon of steam, and held that water, instead of being a primary was only a secondary cause of them—the primary cause being the rolling up of the lava in consequence of pressure due to a slight contraction of the earth's crust. The contact of this fluid lava with the water stored in the crevices is followed by a flush of steam, and this by an influx of water from underlying strata. These are converted into steam and expelled, and the exhausted strata serve as a channel for the influx of sea water into the volcano. A point is finally reached when by the cessation of the shocks and excessive drainage the flow of lava is effected quietly. A paper on Regional Metamorphism, read to the Royal Society in 1885, presented a theory that there exists, in the compression and motion of the strata which have always accompanied the upheaval of mountain chains, a true cause for the development of an amount of heat sufficient to produce one form of metamorphosis—a form which can affect only particular regions—and he would, therefore, in order to distinguish it from contact and normal metamorphism, designate it as regional metamorphism.
Some of Professor Prestwich's later views respecting the Glacial period were presented at a meeting of the Geological Society in May, 1887, when, after showing how the discoveries in the valley of the Somme and elsewhere, twenty-eight years before, had led geologists who had previously been disposed to restrict the age of man to exaggerate the period during which the human race had existed, he proceeded to discuss the views of Dr. Croll on the date of the Glacial period. In view of the recent observations in Greenland of Professor Helland, Mr. Steenstrup, and Dr. Rink, showing that the movement of ice in large quantities was much more rapid, and consequently the denudation produced was much greater than had formerly been supposed, he was disposed to limit the duration of the Glacial epoch to from fifteen to twenty thousand years, including in the estimate the time in which the cold was increasing, or Preglacial time, and that during which it was diminishing, or Postglacial time. Details were given to show that the estimate of one foot on an average being removed from the surface by denudation in six thousand years, on which estimate the hypothesis that eighty thousand years had elapsed since the Glacial epoch was founded, was insufficient, as a somewhat heavier rainfall and the disintegrating effects of frost would produce far more rapid denudation. It was incredible that man should have remained physically unchanged during so long a period. At the same time, evidence that had been brought forward of the occurrence of human relics in Preglacial times had led the author to change his views as to the age of the high-level gravels in the Somme, Seine, Thames, and Avon Valleys, and he was now disposed to assign these beds to the early part of the Glacial epoch, when the ice sheet was advancing. This advance drove the men who then inhabited western Europe to localities which were not covered with ice. Man must, however, have occupied the country but a short time before the land was overwhelmed by the ice sheet. The close of the Glacial epoch, or the final melting of the ice sheet, might have taken place between eight and ten thousand years ago.
His latest and most matured views on this subject, agreeing substantially with these expressions, were embodied in his book, Geology: Chemical, Physical, and Practical, which was published in 1886 and 1888. In these volumes he gave more positive expression to the view which had been for some time assuming shape with geologists, and the acceptance of which had been made imperative by the results of geological surveys in America, that, while the great time divisions of geology may be of almost universal application, the smaller breaks in continuity, which are of frequent occurrence in all areas, are subject to constant differences of extent and value. Consequently, in filling up the details of the several geographical areas, each one is found to have its own local stamp, and possesses its own special terms, some knowledge of which is as essential to the geologist as the language of a country is to the traveler, if he would pass through it with profit.
In the preface to this work Professor Prestwich gave a clearer definition of his attitude toward the different schools of geological thought, observing that the doctrine of non-uniformity must not be confounded with reliance on catastrophes, and that it does not involve any questions respecting uniformity of law, but only those respecting uniformity of action. "I myself," he says, "have long been led to conclude that the phenomena of geology, so far from showing uniformity of action in all time, present an unceasing series of changes dependent upon the circumstances of the time; and that while the laws of chemistry and physics are unchangeable and as permanent as the universe itself, the exhibition of the consequences of those laws in their operation on the earth has been, as new conditions and new combinations successively arose in the course of its long geological history, one of constant variation in degree and intensity of action."
In a lecture at the Victoria Institute in 1894, and in his book, published in 1895, on Certain Phenomena belonging to the Close of the Last Geological Period and on their Bearing upon the Tradition of the Flood, Professor Prestwich presented various phenomena which had come under his observation during long years of geological research throughout Europe and the coasts of the Mediterranean as "only explicable upon the hypothesis of a widespread and short submergence of continental dimensions, followed by early re-elevation; and this hypothesis," he added, "satisfies all the important conditions of the problem."
It will be observed that Professor Prestwich occupied a kind of independent position as a geologist, identified especially with no school, but forming substantially a school by himself. His publications, therefore, often embodied views different from the conclusions which his fellow-geologists had reached; or, to paraphrase an expression of his own, while they were all generally of one opinion as to the main facts of geology, in respect to the explanation of many of those facts they held very divergent opinions. This fact gave name and character to his last book—Collected Papers on Some Controverted Questions of Geology—which was published in 1875. It contained six essays, the first of which was devoted to the clear definition of the author's attitude with respect to the doctrine of uniformity, and the others were in criticism of the astronomical theory of Glacial epochs; the character, age, and make of the flint implements of the chalk plateau of Kent; the agency of water in volcanic eruptions; the thickness and mobility of the earth's crust; and underground temperatures. While these articles were all controversial, the book, as Professor Judd well said in reviewing it, "might fairly be cited as an example of the spirit in which scientific discussions ought to be carried out. No geologist who takes up this work but will find cherished ideas reasoned against or pet notions boldly assailed. But from beginning to end of the volume he will find that no word has been written which is calculated to give pain to the most sensitive opponent." In a similar spirit he exhorted the International Geological Congress in 1888: "Let us try to avoid that error of congresses—of arrogating an infallibility which is little in accord with the progress of science."
Nature, reviewing Professor Prestwich's book on geology in 1886, characterized him as the acknowledged master of British geology, of whom it might be safely affirmed that no living geologist had contributed in a greater degree to the advance of science by his important original researches.
Sir Joseph Lister, speaking in the Royal Society of his death, said that in him "we have lost about the last link that remained which connected geologists of the present day with the founders of the science in the first half of the century. To him we are indebted not only for the first comprehensive classification of the Tertiary beds of this country, to which he assigned the names by which they will henceforth be universally known, but also for their connection with the strata of the Paris basin. To him also is due the credit of having been the first to establish the authenticity of the remains of human workmanship found in the drift deposits of the valley of the Somme, and of thus having laid secure foundations on which arguments as to the extreme antiquity of man upon the earth may be based. In France his name is known and respected as much as in England, and it would be hard to say how much of the advance in geological knowledge during the last sixty years was not due to his unremitted labors, which extended over the whole of that period."
Professor Prestwich retired from the professorship at Oxford in 1888, and spent the rest of his life at his country home in Shoreham, working till almost his last day with undiminished activity. The list of his papers in the catalogue of the Royal Society includes seventy-seven titles, to say nothing of his contributions to other societies and journals. He was elected a fellow of the Royal Society in 1853; was appointed its vice-president in 1870; was president of the Geological Society in 1870; obtained the Wollaston medal of the Geological Society in 1849, and the Royal medal of the Royal Society in 1865; was president of the International Geological Congress in 1888; and was correspondent of the Institute of France, and foreign member of the Accademia dei Lyncei, Rome, the Imperial Geological Institute of Vienna, the Royal Academy of Brussels, the American Philosophical Society, and other learned bodies.