PORTRAITS

AND

BIBLIOGRAPHICAL NOTICES

Contributors to the Science of Geology 

from Antiquity through the Nineteenth Century


These Biographical notes are taken from Karl Alfred von Zittel, History of Geology and Palæontology to the End of the Nineteenth Century, published in 1901, with additional entries as noted.
page
name
notes
3
Xenophanes of Colophon (born 614 B.C.)
observed the shell remains of pelagic mollusca on mountains in the middle of the land, impressions of laurel leaves in the rocks of Paros, as well as various evidences of the former presence of the sea on the ground of Malta, and to have attributed those appearances to periodic invasions of the sea during which men and their dwellings must have been submerged.
3
Xanthus of Sardis (circa 500 B.C.)
drew attention to the occurrence of fossil shells in Armenia, Phrygia, and Lydia, far from the sea, and concluded that the localities where such remains occur had been formerly the bed of the ocean, and that the limits of the dry land and the ocean were constantly undergoing change.
3
Herodotus (born 484 B.C.)
mentioned the presence of fossil shells of marine bivalves in the mountains of Egypt and near the oasis of Ammon. From this fact, as well as from the salt constitution of the rocks, Herodotus formed the opinion that Lower Egypt had been at one time covered by the sea, and that the material carried down by the Nile had been discharged into the sea-basin between Thebes and Memphis and the present delta, and gradually filled it up.
4
Heraclitus (born 535 B.C.)
although the universe always had been and always would be, no portion of it had ever been quiescent, and that from time to time a new world was constructed out of the old.
5
Empedocles of Agrigentum (492-432 B.C.)
the earth's centre was composed of molten material. Empedocles formed this opinion on the basis of his actual observation of the volcanic activities of Mount Etna.
7
Eratosthenes (276-196 B.C.)
by his measurement of the degree in Egypt for the first time laid the foundation of a more exact estimate of the size of our planet. Eratosthenes taught that the changes of form accomplished by means of water, by volcanoes and earthquakes, and by fluctuations of the sea, are insignificant in proportion to the size of the whole earth.
8
Strabo (born circa 63 B.C)
His geography, comprising seventeen volumes, was written about the beginning of the reign of Tiberius. In reference to the occurrence of the above-mentioned fossils in the Libyan desert, he agreed with the Greek philosophers that the sea had once covered certain portions of the land, but he also pointed out that the same district may sometimes rise, some times sink, and fluctuations of the sea-level are associated with such movements of land-surfaces. He further taught that elevations and subsidences of the land are not confined to individual rocks or islands, but may affect whole continents...the town of Spina, near Ravenna, formerly a seaport, was now ninety stadia inland. Strabo is therefore rightly regarded as the father of modern theories of mountain-making, and we owe to him, moreover, the hypothesis that volcanic outbursts act as safety-valves for the pent-up activities of subterranean vapours.
9
Seneca (2 or 4 B.C.-65 A.D.)
Seneca explains earthquakes partly as a result of the expansion of gases accumulated in the earth, partly by the collapse of subterranean cavities. He regards volcanic eruptions simply as an intensified form of the same series of phenomena, and volcanoes themselves as canals or vents between local sub-terrestrial reservoirs of molten material and the earth's surface. He regards the earth as primitively a watery chaos, and it is more especially in his treatment of the action of water in dissolving and carrying away rock-material, together with his explanation of the origin of sediments and deltas, that Seneca has shown his remarkable insight and sound judgment.
9
Pliny the Elder (23-79 A.D.)
Historia Naturalis, in thirty-seven books. Died observing the first outbreak of Vesuvius in 79 A.D.
14
Leonardo da Vinci (1452-1519)
He had in his youth been engaged as an engineer in the construction of canals in North Italy, and had then seen numerous fossils in position in the rocks. The opinions he formed regarding them are remarkable for their clearness and correctness. Leonardo said that the marine organisms scattered in the earth in the form of fossils had actually lived where we now find them.The sea at that time covered the mountains of North Italy: the river-mud brought to the sea from Alpine lands filled the shells of dead mussels or snails, and accumulated on the sea-floor; afterwards the mud deposits became dry land, and the fossils found in them were the casts of the ancient cells.
14
Hieronymus Fracastoro (1483-1553)
practised medicine as a physician in Verona, and in his capacity of physician to Pope Paul III. was a member of the Council of Trent.
Fracastoro repudiated the doctrine of a vis plastica in the earth as impossible; and just as little did he give credence to the view that explained fossils as creatures left by the great Flood. The Flood, he said, was of short duration, and in the nature of things it would have left not marine but fresh-water mussels behind; further, on the assumption that the mussels had been carried from the ocean to the land by the Flood, their remains would have been scattered over thesurface of the land, and would not have been buried deep in the earth where the quarrymen had found them. There was left, he continued, only one possible explanation — that the fossils were the remains of animals which had once lived in the localities where their remains are now imbedded.
15
Agricola (George Bauer) (1494-1555)
He went to Italy, where he graduated as doctor, and then settled in Joachimsthal as a physician; afterwards he was appointed professor of chemistry at Chemnitz, and died there 1555.Werner calls him the father of metallurgy, and the originator of the critical study of minerals. His great work, De re metallica libri duodecim, contains a complete description of mining and metallurgy as then practised. Two later works, De natura fossilium, Lib. x., and De veteribus et novis metallis, Lib. ii., describe all the minerals known to the ancients, and all those which had since been discovered. Agricola referred by far the greater part of the organic remains found in the solid rock to a wholly inorganic origin; he regarded fossil mussels, belemnites, "Ammon's Horns," "Glossopetra" (fish teeth), and other problematical remains as "solidified accumulations from water," analogous with marble and limestone.
17
Martin Lister (1638-1711)
highly respected in York and London as a medical man. In 1698 he accompanied the English ambassador, Lord Portland, to Paris, in 1709 became house physician to Queen Anne. laid down the important principle that the different rocks might be distinguished according to their particular fossil contents, although, strange to say, he thought the rocks themselves had the power to produce the different forms of fossils. Lister warmly combated the idea that the fossils could have proceeded from animals (Philos. Trans. Roy. Soc. London, 1671).
19
Robert Hooke (1635-1703)
English physicist and mathematician. It was he who for the first time suggested the use that might be made of fossils, in revealing the historical past of the earth. Many fossil Ammonites, Nautilids, and other conchylia undoubtedly differed from known living forms, but he said it had to be remembered how scanty was the existing knowledge of marine animals, especially of those which inhabited the greater ocean depths. Hooke, however, inclined to the opinion that the fossils of unknown forms might really be extinct species, annihilated by earthquakes. He regarded it as certain that a number of fossil species had been confined to definite localities. And from the occurrence of fossil Chelonias and large Ammonites in the strata of Portland Isle, Hooke concluded that the climate of England had once been much warmer. His explanation of the elevated position in which fossil marine organisms are now found was based upon his theory of earthquakes. Earthquakes, he thought, transformed plains into mountains, and continents into ocean basins. He attributed earthquakes and volcanic eruptions to the agency of subterranean fire.
21
Johann Ernst Immanuel Walch (1725-78)
Professor of Philosophy and Poetry in Jena. In 1759 Walch succeeded his father as Professor, but his chief delight was in Mineralogy and Palæontology, and he made a famous collection. The outstanding work of this period is undoubtedly that of Knorr and Walch in four volumes, Die Sammlung von Merkwürdigkeiten der Natur und Alterthümer des Erdbodens. The first volume was written by the Nürnberg collector and artist, George Wolfgang Knorr (born 1705, died 1761), and the other three volumes were prepared after the death of Knorr by Professor Walch.
24
Giordano Bruno (????-1600)
Burned at stake for heresy. Bruno described the earth as a spherical body, on whose surface the depths of the oceans were greater than the height of the mountains; the mountains were no higher in proportion to the size of the earth than the wrinkles on the skin of a dried apple.Bruno also denied that there had ever been a universal Deluge, but brought forward evidences of frequent alteration in the distribution of land and sea. He also directed attention to the position of volcanoes in the immediate proximity of the sea, and from that he argued that thermal and volcanic phenomena might be due to some interaction between surface waters and the interior of the earth. Bruno's ideas were not understood by his contemporaries and were neglected.
24
Athanasius Kircher (1602-1680)
Jesuite; teacher of Mathematics in the Collegium Romanum in Rome. There he founded a valuable natural history collection, which was afterwards described by Bonanni in 1709 under the name of Museum Kircherianum, and is still kept up in Rome. His famous work, Mundus subterraneus, Kircher's idea is that there are innumerable subterranean centres of conflagration (pyrophylacia) which are connected with active volcanoes; similarly that there are special water cavities in the earth (hydrophylacia), which are fed from the sea and are connected by branches in all directions with the earth's surface, at which they appear as thermal springs. The first observation of the steady increase of temperature with added depth.
25
Nikolaus Steno (1638-1687)
Steno begins his work on the earth's crust by comparing fossil teeth found in the deposits of Tuscany with the teeth of living sharks. He then investigates the origin of fossiliferous deposits and compares them with unfossiliferous rocks. The latter, he says, were formed before life existed on the earth, at a time when the earth was enveloped in a universal ocean.Steno was the first to enunciate definite natural laws governing the formation of a stratigraphical succession in the earth's crust; these may be condensed as follows : — (1) a definite layer of deposit can only form upon a solid basis; (2) the lower stratum must therefore have consolidated before a fresh deposit is precipitated upon it; (3) any one stratum must either cover the whole earth, or be limited laterally by other solid deposits; (4) during the period of accumulation of a deposit there is above it only the water from which it is precipitated, therefore the lower layers in a series of strata must be older than the upper.Mountains, he said, might also originate from upward action of the volcanic forces in the crust.
29
 John Woodward (1665-1722)
Professor at Gresham College in London. He strongly opposed the opinion that fossils could be mere imitative sports of nature, and said they represented past faunas and floras. But he supposed these remains to have been carried to their present position in the earth by a universal flood, the deluge of the Scriptures.The earth's crust was entirely disintegrated by this catastrophe, but living creatures, plants, and metals remained intact.
30
William Whiston (1666-1753)
his Theory of the Earth ran through six editions in a very short time. He supposed the earth had originally been a comet, which happened to approach the sun, and was melted into a coherent mass. As it travelled away from the sun, a re-arrangement of the earth's material began; the heavier particles formed a solid nucleus, the lighter particles gathered in the superficial parts; the surface was covered by water except where high mountain chains and islands rose above the ocean-level.
31
Antonio Vallisneri (1661-1730)
Professor of Medicine at Padua. an enthusiastic fossil-collector, and entered strong protest against the idea that the Flood was accountable for the annihilation of all pre-existing organisms. His writings point out that marine deposits are widely distributed in Italy at both sides of the Apennines, and are also present in Switzerland, Germany, England, Holland, and other lands, and Vallisnieri therefore argues that those deposits prove incontestably the former presence of the sea over these localities. He favours Strabo's doctrine, and explains how different areas of the earth's surface may have frequently undergone relative changes of level, how portions which are now dry land may formerly have been under sea-water. He further explains the presence of marine fossils in these deposits, on the natural assumption that the inhabitants of the sea as they died fell to the bottom, and were there incorporated in the deposits.
32
Antonio Lazzaro Moro (1687-1740)
His doctrine was that the fossils found in the mountains had originated where they were found, and that the mountains themselves had been upheaved from the sea by volcanic action. All continents and islands had also been upheaved in this way. The stratified material composing some mountains represented the original volcanic ejections, which in consolidating had assumed a certain stratification of a secondary character
32
Benoît De Maillet (1656-1738)
the Telliamed  (anagram of the author). Telliamed was written in  1715 and 1716, but did not appear until 1748. On account of its heterodoxy, De Maillet would not allow its publication until after his death. Whereas Moro attributed all continents, mountains, and islands to volcanic agency, De Maillet regards all the rocks of the earth as marine deposits. The highest or primitive mountain-systems emerged from the world-ocean at a time when the seas were very sparsely inhabited by organisms, hence these rocks are either unfossiliferous or poorly fossiliferous. By the erosion and fragmentation of these primitive rocks the material for the further formation of rock was obtained. Sediments were continually in process of deposition in the seas, and the younger the rocks, the more richly they became filled with the remains of animals and plants. Telliamed also notes that many species of fossil mollusca are apparently now extinct.
36
G. Christian Füchsel (1722-73)
physician in Rudolstadt. Füchsel recognised nine formations in Thuringia from the oldest or fundamental rocks to the Muschelkalk. Füchsel carefully observed and described the fossils characteristic of the Muschelkalk, Buntsandstein, the Zechstein, and other series. laid the foundation of that rapid development of stratigraphical geology which began in Germany in the next generation. He gave to the geological formation a definite palæontological value, and also represented the surface outcrop of the several formations upon an orographical map by means of corresponding signs, letters, or numbers. Füchsel's geological maps were the first of the kind in Germany, and his text was further illustrated by detailed geological sections.
37
Giovanni Arduino (1713-95)
Director of Mines in the Vicentine Province and in Tuscany, afterwards Professor of Mineralogy at Padua. He was the first who sub-divided the stratified rock-succession into Primitive, Secondary, and Tertiary groups.
38
Gottlieb Gläser
The first coloured geological map was published by Gottlieb Gläser at Leipzig in 1775.
41
 George Louis Leclerc de Buffon (1707-1788)
Director of the Botanical Garden at Paris. Buffon there enumerates five "facts" of first importance, and five additional "monuments" or comments. The "facts" are physical in character; they postulate the oblate-spheroidal form of the earth; compare the small amount of heat received from the sun with the large supply possessed by the body of the earth; the effect of the earth's internal heat in altering the rocks of the crust; and the presence of fossils everywhere over the earth, even on the tops of the highest mountains. The "monuments" assert that all limestones consist of the remains of marine organisms, and that in Asia, America, and the North of Europe the remains of large terrestrial animals occur at a small depth below the surface, showing that they apparently dwelt in these regions at no very remote age; whereas the deeper-lying remains of marine creatures in the same region belong to extinct species, or are related only to forms now inhabiting far distant seas.
Buffon's merit consists in the bold construction and masterly exposition of a theory which for the first time brought the historical possibilities of geology to the forefront. His calculation of the duration of the successive epochs had, it is true, no empirical basis. Yet it made sufficiently clear to all readers the author's desire to insist upon long periods of time for the slow processes of change in the earth's configuration, and for the appearance of successive forms of plant and animal life. Some of the noteworthy advances made by Buffon were the differentiation which he drew between the primitive rocks formed in the second period, and the sedimentary and volcanic rocks of the next periods; his clear conception that the oldest inhabitants of the ocean had become extinct and been succeeded by younger forms; his allocation of the early home of the large Mammalia in Polar districts; and his belief, based upon the distribution of land faunas, that the Old and New Worlds had once been united as a wide Northern Continent.
46

THIRD PERIOD 1790-1820
49
Peter Simon Pallas (1741-1811)
 His geological views are contained in a treatise published by the St. Petersburg Academy, Consideration of the Structure of Mountain-Chains (1777), and in the Physical and Topological Sketches of Taurida (1794).

The turning-point in his career was an invitation to fill the chair of Natural History in the Imperial Academy of St. Petersburg, and the further request that he should undertake the leadership of an expedition to Siberia, planned by Empress Catherine II. Pallas spent six years of great privation (1768-74) in Eastern Russia and Siberia, exploring the plains, rivers, and lakes, with a view both to their geography and to their faunas and floras, and he also examined geographically the Ural and Altaï mountains. Pallas published a three-volume work containing an account of his travels and observations. Few explorers have contributed such a vast wealth of geographical, geological, botanical, zoological, and ethnographical observations as Pallas has done in this justly famous work.



52-4
Horace Benedicte de Saussure (1740-1799)
scion of a noble and rich patrician family which had already won high scientific repute in the previous century, De Saussure enjoyed in his early years and education every advantage of wealth, culture, and influence.Professor of Philosophy at the Academy of Geneva. In 1787, at the head of a well-equipped party, he carried out the first ascent of Mont Blanc. between 1789 and 1792, he climbed the summits of Monte Rosa, the Breithorn and Rothhorn. His great work, Voyage dans les Alpes, is a model of clear language, exact observation, absence of bias, and cautious reserve in forming general conclusions.
56
Abraham Gottlob Werner (1749-1817)
He belonged to a family which had been actively engaged in the mining industry for three hundred years. His father, who was overseer of a foundry for hammered iron work, taught him in his boyhood to recognise nearly all the known minerals and after a short period of residence at a school in Silesia, Werner returned to take part in the same foundry as his father. in 1774 published his first paper on "The External Characteristic Features of Fossils." In 1775 Werner was appointed Inspector of Collections and teacher in the School of Mines at Freiberg. This post he held for more than forty years,

The most trustworthy reports of Werner's "geognosy" are probably those written by Franz Ambros Reuss in the third part of his text-book (Leipzig, 1801-3); by D'Aubisson de Voisins in his Traité de Géognosie (Strasburg and Paris, 1819); and by Jameson in the Elements of Geognosy (Edinburgh, 1808). Werner himself published only one lecture — "Introductory to Geognosy" — delivered at Dresden.

Werner defined "Geognosy" as the "Science which inquires into the constitution of the terrestrial body, the disposition of fossils (i.e. minerals, cf. p. 15) in the different rock layers, and the correlation of the minerals one to another." Neptunianism.
61
Leopold von Buch (1774-1852)

Leopold von Buch was the most illustrious of the geologists taught by Werner. Leopold von Buch was rightly regarded as the greatest geologist of his time. He had studied in every domain of geology; he was familiar with a large part of Europe. Wherever he went, he willingly and freely communicated his own knowledge to others, and ever rejoiced to be able to assist by his money or his influence any one in whom he detected a true devotion to science. The later writings of Leopold von Buch, published between 1820 and 1860, are those on which his fame chiefly rests; but from the year 1796 he was actively engaged in travel and research, and his earlier writings contributed in a great degree to establish the science of geology.  Accompanied by the English botanist, Charles Smith, he visited the Canary Isles, and in 1815 convinced himself that they had been the centre of intense volcanic activity. In his famous monograph, A Physical Description of the Canary Islands, published in 1825, he enunciated his hypothesis of upheaval craters, and distinguished between "centres" and "bands" of volcanic action.  In 1832 Von Buch edited a geological map of Germany, and this magnificent work had already run through five editions in  1843. A complete edition of his works was published after his death at Berlin (1867-77).


64
Alexander von Humboldt (1769-1859)
born in Berlin in 1769, studied at first in Göttingen, afterwards in 1791-92 with Werner at Freiberg. On the completion of his studies he was made Director of Mines, and moved from Bayreuth and Ansbach to Steben in the Fichtel mountains.  Humboldt's best contributions to geology were his investigation of volcanoes and earthquakes, and the broad generalisations which he drew regarding volcanic action. In the summer of 1804 he returned by Havana and North America to Paris. There he became at once absorbed in physical and chemical studies, conducted along with Biot, Gay Lussac, and Arago, and he also

commenced the publication of his great work, Travels in the Equinoctial Regions on the New Continent. This work comprises twenty volumes; but although there were several collaborators, the work was never quite completed, and the expenses in connection with it swallowed up the remainder of Von Humboldt's means. In the spring of 1805 he visited Italy, and with his friends, Gay Lussac and Leopold von Buch, saw an eruption of Vesuvius.  Humboldt's account of the catastrophe in the year 1759, which gave birth to the Jorulla and five other mountains, and covered an area of four square miles with a mass of lava, sand, and slag five hundred feet high, still ranks as one of the most noteworthy contributions in the whole literature of volcanoes.
During nearly twenty years' residence in Paris (1808-27) he published the series of papers which form the groundwork of his Views of Nature, and also a special geological work entitled Geognostic Essay on the Trend of the Rocks in the Two Hemispheres (Paris, 1822). This work practically marked the conclusion of Humboldt's literary activity in geology. Upon his return to his native city of Berlin in 1827, Humboldt embarked upon his gigantic plan of producing a physical description of the world. Twenty years passed before this plan was realised and his famous work, The Cosmos, appeared.


70
James Hutton (1726-1797)

Hutton was the first to demonstrate the connection of eruptive veins and dykes with deeper-seated eruptive masses of granite, and the first to point out the differences of structure between superficial lavas and molten rock solidified under great pressure. In assuming that granite represents rock consolidated from a molten magma, Hutton laid the foundation of the doctrines of Plutonism as opposed to those of Neptunism.

Hutton's genius first gave to geology the conception of calm, inexorable nature working little by little — by the rain drop, by the stream, by insidious decay, by slow waste, by the life and death of all organised creatures, — and eventually accomplishing surface transformations on a scale more gigantic than was ever imagined in the philosophy of the ancients or the learning of the Schools. And it is not too much to say that the Huttonian principle of the value of small increments of change has had a beneficial, suggestive, and far-reaching influence not only on geology but on all the natural sciences. The generation after Hutton applied it to palæontology, and thus paved the way for Darwin's still broader, biological conceptions upon the same basis

Hutton was thus the great founder of physical and dynamical geology; he for the first time established the essential correlation in the processes of denudation and deposition; he showed how, in proportion as an old continent is worn away, the materials for a new continent are being provided, how the deposits rise anew from the bed of the ocean, and another land replaces the old in the eternal economy of nature. The outcome of Hutton's argument is expressed in his words "that we find no vestige of a beginning, — no prospect of an end." 

When we compare Hutton's theory of the earth's structure with that of Werner and other contemporary or older writers, the great feature which distinguishes it and marks its superiority is the strict inductive method applied throughout. Every conclusion is based upon observed data that are carefully enumerated, no supernatural or unknown forces are resorted to, and the events and changes of past epochs are explained from analogy with the phenomena of the present age.

His strong bent for chemical science induced him to select medicine as a profession. He studied at Edinburgh, Paris, and Leyden, and took his degree at Leyden in 1749 but on his return to Scotland he did not follow out his profession. Having inherited an estate in Berwickshire from his father, he went to reside there, and interested himself in agriculture and in chemical and geological pursuits. in 1785 read his paper on the "Theory of the Earth" before the Royal Society of Edinburgh. Three years later it was published in the Transactions.

The original treatise of Hutton is divided into four parts. The first two parts discuss the origin of rocks. The earth is described as a firm body, enveloped in a mantle of water and atmosphere, and which has been exposed during immeasurable periods of time to constant change in its surface conformation. The events of past geologic ages can be most satisfactorily predicted from a careful examination of present conditions and processes. The earth's crust, as far as it is open to our investigation, is largely composed of sandstones, clays, pebble deposits, and limestones that have accumulated on the bed of the ocean. The limestones represent the aggregated shells and remains of marine organisms, while the other deposits represent fragmental material transported from the continents. In addition to these sedimentary deposits ot secondary origin there are primary rocks, such as granite and porphyry, which, as a rule, underlie the aqueous deposits.


73
Sir James Hall (1762-1831)
Hall; in his desire to vindicate Hutton's theory, became himself one of the great founders of experimental geology.
74
John Playfair (1748-1819)

Mathematician. son of a minister, showed in his early years a remarkable genius for mathematics. He studied in Aberdeen and Edinburgh, in 1773 became minister in Bervie, in 1785 Professor of Mathematics in the University of Edinburgh, and twenty years after Professor of Philosophy in the same University Led by Hutton into the study of geology, he devoted his holidays to geological tours throughout Great Britain and Ireland, and in 1815 and 1816 made longer tours to Auvergne, Switzerland, and Italy

Playfair's Illustration of the Huttonian Theory (1802) is a lucid exposition of that theory in the form of twenty-six ample discussive notes. Playfair's work differs in no essential point from the views held by his master and friend, but many subjects which receive a subordinate treatment in the Theory of the Earth are brought into prominence by Playfair, and placed for the first time on a firm scientific basis.


89
Baithazar Hacquet
(1739-1815)
Born in Brittany, he became a surgeon; in that capacity he attached himself to the Austrian Army throughout the Seven Years' War. At the close of the war he taught Surgery at the Lyceum of Laibach, and in 1788 he was made Professor of Natural History and Surgery in the University of Lemberg.
91
John Gotifried Ebel (1764-1830)
studied medicine, then travelled three years in Switzerland, and in 1793 settled as a physician at Frankrort-on-Main he published a "Guide," How to Travel in Switzerland in the most Pleasant and Practical Way (4 parts, 1793), a work which has served as the pattern of our present guide-books for travellers. His next work was A Description of the Mountain=peoples of Switzerland, 1798-1802. His chief geological work, On the Structure of the Earth in the Alpine Mountain-System, was published at Zurich in 1808.
95
Giovanni Battista Brocchi (1772-1826)
Professor of Natural History in Brescia, and afterwards Inspector of Mines for the Kingdom of Italy. Brocchi's ideas about the mode of extinction and period of existence of fossil genera and species are of especial interest. He opposes the Catastrophal Theory, which taught that from time to time destructive catastrophes had occurred in past ages, and had annihilated the whole or the greater portion of existing forms; and he lays down principles of the evolution of one from another along continuous lines of descent, but in accordance with definite natural laws of growth and decay. He argues that just as a definite span of life is meted out to each individual, and the time may be longer or shorter according to the kind of organisation, in the same way each species and each genus possesses a definite energy of existence, and when that has been exhausted, death ensues from natural causes of decay.
96
Guy S. Tancrède de Dolomieu (1750-1801)
officer in the army; he travelled for several years in Sicily, South and Central Italy, the Pyrenees and Alps; in 1796 he was elected a Professor in the Paris School of Mines, and accompanied the French Expedition to Egypt. XVhile on the return journey he was taken into custody, for political reasons, in Naples, and was imprisoned for two years. After he regained his liberty he became, in 1800, Professor of Mineralogy at the Natural history Museum in Paris, but died in the following year in Paris. His most important works are: Travels in the Lipari Isles (Paris, 1783); On the Earth-Tremors in Calabria (Rome, 1784); On the Lepontine Isles, and a catalogue of the Products of Etna (Paris, 1788).

Dolomieu confirmed the igneous origin of basalt rock, regarding it as a variety of lava for the most part associated with submarine eruptions. He compared the alternating lava streams and sedimentary strata at Etna with the stratigraphical relations of the so-called trap-rocks in the Vicentine district, and concluded that the latter gave evidence of volcanic activity.

The name of Dolomieu is perpetuated in the name of the "Dolomites," given to the beautiful district in South Tyrol south of the Puster Valley. Dolomieu called attention in 1791 to the unusual mineralogical character of the "Alpine limestone" in that district. His chemical investigations proved the rock to contain, in addition to lime carbonate, a very high percentage of magnesium carbonate; so that the rock could by no means be regarded as a true limestone. Afterwards, any highly magnesic limestone came to be called "Dolomite" rock.

In 1797 Dolomieu confirmed the statement of Giraud Soulavie, that the volcanoes of Auvergne and Vivarais are intruded into the granite, and partially rest upon it. Thus Dolomieu extended our knowledge of the mineralogical  composition of rocks on many definite points, and his researches at once gained recognition. Italian geologists applied themselves with fresh zeal to the study of their volcanic rocks, working more by the practical methods of Dolomieu. Soon they discovered the weaknesses in Dolomieu's writings, where that keen observer had ventured to speculate on the causes which might determine the particular setting and orientation of mineral material characteristic of the transitional varieties of igneous rocks.        


98
Lazzaro Spallanzani (1729-1799)
Professor of Natural History in Pavia, was the first who applied experimental methods to the elucidation of volcanic rock-structure. He set up series of experiments in his laboratory in order to find out whether gaseous vapour would escape when lava was melted, and what was the chemical nature of such vapours. The result showed that little gas escaped, but the powdered lava partially sublimated, and was partially converted into a vesicular rock-mass.

Spallanzani then tested Dolomieu's idea that the crystalline structure of volcanic rocks was produced under the influence of a moderate degree of volcanic heat acting during a long period. Different kinds of lava were exposed to definite tempera tures for forty-five days, some even for ninety days. The result of Spallanzanrs experiment appeared negative, since a moderate heat acting for a long time produced precisely the same effects as a more intense heat acting for a shorter period.

Spallanzani also investigated whether, in accordance with the hypothesis of Dolomieu, the presence of sulphur would hasten the fluidity of the lava, and whether the melted material in this case would solidify as a crystalline, rough-grained, or vitreous rock. The result was again negative. The powdered specimens of lava mixed with sulphur demanded the same time to become fluid as the specimens with which no sulphur had been mixed, and on solidifying produced the same glassy rock. Spallanzani therefore opposed Dolomieu's theory, that a combustible substance was present in flowing lava, pointing out (1) that no flames had ever been seen on the surfaces of lava streams; (2) that all lavas were easily brought back to a fluid condition; whereas if Dolomieu were right in supposing they became solid after all the combustible material had been consumed, then in the absence of the latter it should be much more difficult to melt the lavas.

Spallanzani's experimental researches were published in several volumes in the same series as the more popular descriptive account of his travels (Travels in Sicily and some parts of the Apennines, 6 vols., Pavia, 1792-97). His descriptions and observations of volcanic regions surpass in scientific accuracy and completeness all previous contributions of the kind, and have secured a permanent place in the literature of scientific travel. Although Spallanzani's numerous experiments invariably produced vitreous rock-varieties, Hall succeeded shortly after in demonstrating that crystalline structure could be produced experimentally by the slow cooling of melted rock.

101
Desmarest (1725-1815)
Desmarest was the French geologist whose genius disclosed the full significance of these extinct volcanoes and made Auvergne famous. 

In 1763 he observed on the plateau of Prudelle, near Clermont, basaltic pillars in close relationship with a lava flow, and he spent many years in collecting facts to prove the volcanic origin of the basalt. The work which he published in the Mémoires de l'Académie royale des Sciences (1774-75) established the igneous origin of basalt without a shadow of doubt. 

Desmarest was himself so entirely convinced of the result of his conclusions that he took no part in the strife between Neptunists and Volcanists, but when questioned by any hesitating adherents of either party he used to reply laconically, "Go and see."


101
Count Reynaud de Montlosier (1755-1838)
published in 1789 an Essay on the Volcanoes of Auvergne, in which he promulgated a new theory about volcanoes. Like Desmarest, Montlosier recognised that there were in Auvergne volcanoes of different ages. The younger have preserved their typical conical form and their craters uninjured. The older are for the most part situated at higher levels, and these characteristic features are absent; they are connected ridges or isolated mountains composed of pillared basalt, or trachytic rocks, frequently reposing on granite. Whereas it is clear that the younger craters and cones of loose ejected material and lava are of true volcanic character, Montlosier claimed for the older and relatively higher groups of igneous rocks that they represented a single upheaval of an extensive viscous mass of rock-material that had then cooled in the elevated position.
103
Johann von Charpentier (1786-1855)
travelled as a young man for four seasons in the Pyrenees (1808-12). The geological work which he published in 1823 was for a long time the standard work upon these mountains. He established for the first time that there was a transverse fault through the whole breadth of the chain between Montrejeau and Perpignan, the eastern part of the chain having been displaced to the north relatively to the western portion.
105
Alexandre Brongniart (1770-1847) and Georges Cuvier (1769-1832)

106
Jean Baptiste Julien d'Omalius d'Halloy (1783-1875)
devoted himself from 1804 to 1814 wholly to the pursuit of geological researches in France, Belgium, and the neighbouring districts; in 1815 was appointed Governor of the Province of Namur; afterwards a Member of the Belgian Senate, and President of the Academy of Sciences in Brussels. he conducted geological tours on foot during ten years, and as a result he was enabled to produce a geological map of France and the adjoining territories of Belgium, Germany, and Switzerland. The map gave a faithful representation of the distribution of the leading geological formations. It was first published in 1822, on the scale of 1:4,000,000, and was in later years improved and incorporated in D'Halloy's Text-book of Geology.
109
William Smith (1769-1839)
William Smith was a self-taught genius of rare originality and with exceptionally keen powers of observation."Father of English Geology." received a scanty elementary education at the village school; managed, however, to train himself to some extent in geometrical studies, and entered at the age of eighteen as an assistant in a Land surveyor's office. He was afterwards employed as engineer in the construction of a canal in Somersetshire, and practised independently as land-surveyor and civil engineer.He laid before the Board of Agriculture a series of memoranda and geological maps which were published between 1794 and 1821 in the form of excellently printed detail-maps of fifteen counties. These maps were on such a large scale, and so full of details, that they had a limited circulation. Smith therefore conceived a plan to publish a geological map of England and Wales on a small scale, that should show accurately the course of the surface outcrop of each stratigraphical horizon, and should be accompanied by geological sections to the true scale of the map. The preliminary sketch of this plan was drawn up in 1801, and may be seen in the Archives of the Geological Society; but it was 1812 before Smith found a publisher to undertake the map. In 1815, the famous map of England and Wales appeared, consisting of fifteen sheets in the scale of 1 inch to 5 miles. The complete map is 8 ft. 9 in. high and 6 ft. 2 in. broad. The individual strata are indicated by different colours, and sometimes the basis of a stratum is marked by a darker line of the ground colour. Smith's map is the first attempt to represent on a large scale the geological relations of any extensive tract of ground in Europe. Smith gave an explanatory text of fifty pages, in which he introduced a stratigraphical terminology adopted from the local names in practical use (Lias, Forest-Marble, Cornbrash, Coralrag, Portland Rock, London Clay, etc.), and these names of horizons have for the most part been retained in geology to the present day.

Between 1816 and 1819, Smith began a work entitled Strata identified by Organised Fossils, containing prints of the most characteristic specimens in each stratum. Four volumes appeared containing the description of sixteen strata and their characteristic fossils, from the horizon of Fuller's Earth to London Clay, but the work was never completed. In 1817 he prepared an ideal geological section across England from London to Snowdon, and the section was afterwards introduced into most text-books.
112
George Bellas Greenough (1778-1855)
founded the Geological Society of London published a geological map of England and Wales in 1819, soon after the appearance of W. Smith's. The original edition appeared in six sheets; in 1826 a reduced map was published and at once obtained a wide circulation. New and improved editions of Greenough's map continue to appear at the present day, and for a long time this map was the best that existed.
113
 John MacCulloch (1773-1835)