Four sciences studied the earth: meteorology explored its envelope of weather; geodesy estimated its size, shape, density, and such distances as involved its surface curvature; geology delved into its composition, depths, and history; geography charted its lands and seas.
Besides the simple rain gauge, the science of weather used four measuring instruments: the thermometer for temperature, the barometer for atmospheric pressure, the anemometer for winds, the hygrometer for moisture in the air.
In or before 1721 Gabriel Daniel Fahrenheit, a German instrument maker in Amsterdam, developed the thermometer, which Galileo had invented in 1603; Fahrenheit used mercury instead of water as the expanding-contracting fluid, and divided the scale into degrees based upon the freezing point of water (32°) and the oral temperature of the normal human body (98.6°). In 1730 René de Réaumur reported to the Académie des Sciences “rules for constructing thermometers with comparable gradations”; he took the freezing point of water as zero, and its boiling point as 80°, and he graduated the scale to make the degrees correspond to equal increments in the rise or fall of the thermometric fluid, for which he used alcohol. Anders Celsius of Uppsala, about 1742, improved Réaumur’s thermometer by returning to the use of mercury, and dividing the scale into a hundred “centigrade” degrees between the freezing and the boiling points of water. By determining these points more precisely, Jean André Deluc of Geneva, in 1772, gave the rival thermometers essentially the form they have today: the Fahrenheit form for English-speaking peoples, the centigrade form for others.
The barometer had been invented by Torricelli in 1643, but its readings of atmospheric pressure were made uncertain by factors for which he had not allowed: the quality of the mercury, the bore of the tube, and the temperature of the air. Various researches, culminating in the experiments and calculations of Deluc (1717–1817), remedied these defects, and brought the mercury barometer into its current form.
Divers crude anemometers were made in the seventeenth century. At his death in 1721 Pierre Huet, the scholarly bishop of Avranches, left a design for an anemometer (the word was apparently his invention) that would measure the force of the wind by funneling it into a tube where its pressure would raise a column of mercury. This was improved by the “wind gauge” (1775) of the Scottish physician James Lind. John Smeaton devised (c. 1750) a mechanism for measuring wind velocity. The best eighteenth-century instrument for measuring moisture was the hygrometer of the versatile Genevan Horace de Saussure (1783), which was based upon the expansion and contraction of a human hair by changes in humidity. William Cullen provided a basis for another type of hygrometer by noting the cooling effect of fluids in evaporation.
With these and other instruments, such as the magnetic needle, science strove to detect regularities in the vagaries of weather. The first requisite was reliable records. Some had been kept for France by the Académie des Sciences since 1688. From 1717 to 1727 a Breslau physician kept daily records of weather reports which he had solicited from many parts of Germany; and in 1724 the Royal Society of London began to compile meteorological reports not only from Britain but also from the Continent, India, and North America. A still wider and more systematic co-ordination of daily reports was organized in 1780 by J. J. Hemmer at Mannheim, under the patronage of the Elector Palatine Charles Theodore; but this was abandoned (1792) during the wars of the French Revolution.
One meteorological phenomenon that sparked much speculation was the aurora borealis. Edmund Halley carefully studied the outbursts of these “northern lights” on March 16–17, 1716, and ascribed them to magnetic influences emanating from the earth. In 1741 Hjorter and other Scandinavian observers noted that irregular variations of the compass needle occurred at the time of the displays. In 1793 John Dalton, the chemist, pointed out that the streamers of the lights are parallel to the dipping needle, and that their vertex, or point of convergence, lies in the magnetic meridian. The eighteenth century, therefore, recognized the electrical nature of the phenomenon, which is now interpreted as an electrical discharge in the earth’s atmosphere, due to ionization caused by particles shot out from the sun.
The literature of meteorology in the eighteenth century began with Christian von Wolff’s Aerometricae elementa (1709), which summed up the known data to date, and suggested some new instruments. D’Alembert attempted a mathematical formulation of wind motions in Réflexions sur la cause générale des vents, which won a prize offered by the Berlin Academy in 1747. The outstanding treatise in this period was the massive Traité de météorologie (1774) by Louis Cotte, a priest of Montmorency. Cotte gathered and tabulated the results of his own and other observations, described instruments, and applied his findings to agriculture; he gave the flowering and maturation time of various crops, the dates at which swallows came and went, and when the nightingale could be expected to sing; he regarded the winds as the chief causes of changes in the weather; and finally he offered tentative formulas for weather forecasts. Jean Deluc’s Recherches sur les modifications de l’atmosphère (1772) extended the experiments of Pascal (1648) and Halley (1686) on the relations between altitude and atmospheric pressure, and formulated the law that “at a certain temperature the differences between the logarithms of the heights of the mercury [in the barometer] give immediately, in thousandths of a fathom, the difference in heights of the places where the barometer was observed.”71 By attaching a level to his barometer, Deluc was able to estimate barometrically the altitude of various landmarks; so he calculated the height of Mont Blanc as 14,346 feet above sea level. Horace de Saussure, after ascending the mountain and taking barometric readings at its peak (1787), obtained a measurement of 15,700 feet.
Geodesy literally meant “dividing the earth.” To do this neatly it was necessary to know the shape of the globe. By 1700 there was general agreement that the earth was not quite spherical but ellipsoidal—flattened a bit at its extremities. Newton thought it was flattened at the poles; the Cassinis held that it was flattened at the equator. To decide this international issue the Académie des Sciences sent out two expeditions. One, led by Charles de La Condamine, Pierre Bouguer, and Louis Godin, went (1735) to what was then Peru (now Ecuador) to measure a degree of astronomic latitude on an arc of the meridian near the equator.VII They found that the distance between one degree of astronomic latitude and the next, on the meridian passing over their place of observation, was 362,800 feet. In 1736 a similar expedition was sent to Lapland, under Maupertuis and Clairaut, to measure a degree of astronomic latitude on an arc of the meridian at a place as near as practicable to the Arctic Circle. It reported that the length of a degree there was 367,100 feet—a little more than sixty-nine miles. These findings indicated that the length of a degree of astronomic latitude increased slightly as the observer moved from the equator toward the pole; and the increase was interpreted as due to the polar flattening of the earth. The Académie des Sciences conceded that Newton had been vindicated. The measurements taken in these expeditions were later made the basis for determining a meter, the metric system, and the precise astronomical time of various localities on the earth.
Bouguer, noting some deflections of the plumb line in the Peruvian observations, ascribed them to the attractive force of the nearby Mt. Chimborazo. By measuring the deflection he estimated the density of the mountain, and on that basis he tried to calculate the density of the earth. Nevil Maskelyne, astronomer royal to George III, pursued the quest (1774–78) by dropping a plumb line now on one side, now on the other, of a granite mountain in Scotland. In both cases the line was deflected some twelve angular seconds toward the mountain. Maskelyne concluded that the density of the earth would bear the same ratio to the density of the mountain as the gravitational force of the earth bore to the twelve seconds’ deviation. On this basis Charles Hutton calculated the earth’s density to be approximately 4.5 times that of water—a figure now generally accepted, which Newton had reached, by a typically brilliant conjecture, a century before.
The study of the origin, age, and constitution of the earth, of its crust and subsurface, of its earthquakes, volcanoes, craters, and fossils, was still hampered by theological taboos. Fossils were generally explained as the relics of marine organisms left on land by the waters receding after Noah’s Flood, which was believed to have covered the globe. In 1721 Antonio Vallisnieri, in his treatise Dei corpi marini che sui monti si trovano, pointed out that a temporary flood could not account for so widespread a deposit of marine formations. Anton Moro, in his volume De’ crostacei e degli altri marini corpi che si trovano su’ monti (Venice, 1740), suggested that the fossils had been thrown up by volcanic eruptions from the sea. Originally the earth had been covered with water; subterranean fires forced up the underlying land above the subsiding sea, and created mountains and continents.
Benoît de Maillet left at his death (1738) a manuscript which came to print in 1748 as Telliamed, ou Entretiens d’un philosophe indien avec un missionaire français. His views were put into the mouth of a Hindu sage, but it soon appeared that “Telliamed” was “de Maillet” reversed; and the storm evoked by the book might have reconciled the author to his timely death. In his theory land, mountains, and fossils had been formed not by volcanic eruptions but by the gradual subsidence of the waters that had once covered the earth. All land plants and animals, Maillet suggested, had evolved from corresponding marine organisms; indeed, men and women were evolved from mermen and mermaids who, like the frog, had lost their tails. The recession of the waters was caused by evaporation, which reduced the sea level by some three feet every thousand years. Eventually, Maillet warned, the oceans will quite dry up, and subterranean fires will come to the surface and consume all living things.
A year after Telliamed Georges Louis de Buffon issued the first of his two magistral contributions to a young science still swaddled in unverifiable speculation. His Théorie de la terre (1749) was written at forty-two, his Époques de la nature (1778) was written at seventy-one. He began with Cartesian caution, by postulating an initial push given to the world by God; thereafter the Théorie offered a purely natural explanation of cosmic events. Anticipating by two centuries the latest theory of cosmogony, Buffon suggested that the planets had originated as fragments detached from the sun by the impact or gravitational pull of some powerful comet; hence all the planets were at first molten and luminous masses, like the sun today, but they gradually cooled and darkened in the cold of space. The “days” allowed for the Creation in the Book of Genesis must be interpreted as epochs. Of these we may distinguish seven:
1. The earth took its spheroidal shape as the result of its rotation, and slowly its surface cooled (3,000 years).
2. The earth congealed into a solid body (32,000 years).
3. Its envelope of vapors condensed to form a universal ocean (25,000 years).
4. The waters of this ocean subsided by disappearing through crevices in the crust of the earth, leaving vegetation on the surface, and fossils at various heights on the land (10,000 years).
5. Land animals appeared (5,000 years).
6. The sinking of the ocean divided the Western from the Eastern Hemisphere, Greenland from Europe, Newfoundland from Spain, and left many islands apparently rising from the sea (5,000 years).
7. The development of man (5,000 years).
Adding these seven ages together, Buffon noted that they came to 85,000 years. He would marvel at the superior imagination of current geologists, who allow the earth a history of four billion years.
Buffon founded paleontology by studying fossil bones and deducing from them the successive epochs of organic life. The first lines of his Époques de la nature display his perspective and his style:
Comme dans l’histoire civile on consulte les tîtres, on recherche les médailles, on déchiffre les inscriptions antiques, pour déterminer les époques des révolutions humaines et constater les dates des événements moraux, de même, dans l’histoire naturelle, il faut fouiller les archives du monde, tirer des entrailles de la terre les vieux monuments, receuillir leur débris, et rassembler en un corps de preuves tous les indices des changements physiques qui peuvent nous faire remonter aux différents âges de la nature. C’est le seul moyen de fixer quelques points dans l’immensité de l’espace, et de placer un certain nombre de pierres numéraires sur la route éternelle du temps. Le passé est comme la distance; notre vue y décroit, et s’y perdrait de même si l’histoire et la chronologie n’eussent placer des fanaux, des flambeaux, aux points les plus obscurs.72 VIII
And then, having come to paleontology only in his advanced years, he wrote:
With sorrow I leave these fascinating objects, these precious monuments of ancient nature, which my own old age gives me no time to examine sufficiently to draw from them the conclusions which I envision, but which, founded only on hypothesis, should have no place in this work, wherein I have made it a law to present only truths based on facts. After me others will come.73
The Époques de la nature was one of the epochal books of the eighteenth century. Buffon lavished upon it all his artistry of style, even (if we believe him) to rewriting some parts of it seventeen times.74 And he poured into it all the power of his imagination, so that he seemed to be describing, across a chasm of sixty thousand years, the constructions of his thought as if they were events unrolling before his eyes.IX Grimm hailed the book as “one of the most sublime poems that philosophy has ever dared to inspire,” and Cuvier pronounced it “the most celebrated of all the works of Buffon, in a style truly sublime.”76
Meanwhile humbler students sought to chart the distribution of minerals in the soil. Jean Guettard won the praise of the Académie des Sciences by his Mémoire et carte minéralogique (1746). While making this first attempt at a geological survey, he discovered extinct volcanoes in France; he explained surrounding deposits as solidified lava, and hot springs as the last stages of these volcanic forces. The Lisbon earthquake stimulated John Mitchell to prepare an Essay on the Causes and Phenomena of Earthquakes(1760); he suggested that they were due to the sudden contact of subterranean fire and water, producing expansive evaporation; this found some outlet through volcanoes and craters, but when such escapes were not available they produced tremors in the surface of the earth; these earth waves, Mitchell suggested, can be plotted to find the focus of the quake. So geology, still young, gave birth to the science of seismology.
Stratigraphy too became a specialty: men puzzled over the origin, composition, and sequence of the strata in the crust of the earth. Coal mines offered an opening to such studies; so John Strachey gave to the Royal Society (1719) “A Curious Description of the Strata Observed in the Coalmines of Mendip in Somersetshire.” In 1762 Georg Christian Füchsel issued the first detailed geological map, describing the nine “formations” in the soil of Thuringia, and establishing the conception of a formation as a succession of strata collectively representing a geological epoch.
Rival theories fought over the causes of such formations. Abraham Werner, who for forty-two years (1775–1817) taught at the Freiberg School of mines, made his professorial chair the popular seat of the “Neptunist” view: continents, mountains, rocks, and strata had all been produced by the action of water, by the subsidence—sometimes slow, sometimes catastrophic—of a once universal ocean; rocks were the precipitation or sedimentation of minerals left dry by the receding sea; strata were the periods and deposits of this recession.
James Hutton added fire to water in explaining the vicissitudes of the earth. Born in Edinburgh in 1726, he became one of that remarkable group—Hume, John Home, Lord Kames, Adam Smith, Robertson, Hutcheson, Maskelyne, Maclaurin, John Playfair, Joseph Black—that constituted the Scottish Enlightenment. He passed from medicine to chemistry to geology, and soon concluded that many times the six thousand years allowed by the theologians would be required for the history of our globe. He noted that wind and water are slowly eroding mountains and depositing them into the plains, and that thousands of rivulets carry off material into rivers, which then carry it into the sea; let this process continue indefinitely, and the grasping figures or raging claws of the oceans could swallow whole continents. Nearly all geological formations might have resulted from such slow natural operations as one might see in any eroding farm or encroaching sea, or any river digging its own bed with patient pertinacity, leaving the record of its falling levels on the strata of rocks and soil. Such gradual changes, Hutton felt, were the basic causes of terrestrial transformations. “In interpreting nature,” he held, “no powers are to be employed that are not natural to the globe, no action to be admitted except those of which we know the principle, and no extraordinary events to be alleged in order to explain a common appearance.”77
But if such erosion has been going on for thousands of millenniums, why are any continents left? Because, said Hutton, the eroded material, accumulating at the bottom of the sea, is subject to pressure and heat; it fuses, consolidates, expands, mounts, emerges from the waters to form islands, mountains, continents. That there is subterranean heat is evidenced by volcanoes. Geological history, then, is a circulatory process, a vast systole and diastole which repeatedly pours continents into seas, and from those seas raises up new continents. Later students named Hutton’s theory “vulcanism,” from its dependence upon the effects of heat, or “plutonism,” from the ancient god of the nether world.
Hutton himself hesitated to publish his views, for he knew that they would be opposed not only by believers in the literal infallibility of the Bible, but quite as sharply by the “Neptunists,” who found an enthusiastic defender in Robert Jameson, professor of natural philosophy in the University of Edinburgh. Hutton confined himself at first to expounding his theory to a few friends; then, at their urging, he read two papers on the subject to the recently established Royal Society of Edinburgh in 1785. Criticism was polite until 1793, when a Dublin mineralogist attacked Hutton in terms that stirred his ire. He replied by publishing one of the classics of geology, Theory of the Earth (1795). Two years later he died. Through John Playfair’s lucid Illustrations of Huttonian Theory (1802), the conception of great changes produced by slow processes passed into other sciences, and prepared Europe for Darwin’s application of it to the origin of species and the descent of man.
But the surface of the earth is more fascinating than its bowels. The progressive exhibition of the diversities of mankind in race, institutions, morals, and creeds was a powerful factor in broadening the borders of the modern mind. Exploration proceeded ever more curiously and acquisitively into the unknown; not for science’s sake but to find raw materials, gold, silver, precious stones, food, markets, colonies, and to chart the seas for safer navigation in peace and war. Even the voyage of the mutinous Bounty (1789) had for its original object the transplantation of the breadfruit tree from the South Seas to the West Indies. The French, the Dutch, and the English competed most eagerly in the game, knowing that the mastery of the world was at stake.
One of the most venturesome explorations originated in the mind of Peter the Great, who, shortly before his death in 1725, commissioned Vitus Bering, a Danish captain in the Russian navy, to explore the northeastern coast of Siberia. The Academy of St. Petersburg appointed an astronomer, a naturalist, and an historian to accompany the expedition. Proceeding overland to Kamchatka, Bering sailed (1728) to 67° north latitude, discovered the strait that bears his name, and then returned to St. Petersburg. On a secondexpedition he built a fleet at Okhotsk, and sailed eastward till he sighted North America (1741); so a Dane discovered that continent from the west as the Norse Leif Ericson had discovered it from the east. On the voyage back Bering’s ship lost its bearings in a heavy fog, and the crew spent six months on a previously uninhabited island near Kamchatka. On that island, which also carries his name, the great Dane died of scurvy (1741) at the age of sixty. Another vessel in the expedition discovered the Aleutian Islands. Russia took possession of Alaska, and missionaries were sent out to acquaint the Eskimos with Christian theology.
The advance of Russia into America stirred other nations to explore the Pacific. As part of a war with Spain (1740) England dispatched a fleet under George Anson to harass the Spanish settlements in South America. Scurvy decimated his crews, and storms off Cape Horn wrecked some of his ships; but he forced his way into the South Pacific, stopped at the Juan Fernández Islands, and found proof that Alexander Selkirk (Defoe’s Robinson Crusoe) had been there (1704–9); then he crossed the Pacific, captured a Spanish galleon near the Philippines, took its treasure of gold and silver ($1,500,000), crossed the Indian Ocean, rounded the Cape of Good Hope, eluded the Spanish and French fleets that sought to intercept him, and reached England June 15, 1744, after a voyage of three years and nine months. The prize bullion was transported from Spithead to London in thirty-two wagons to the accompaniment of martial music. All England acclaimed Anson, and four editions of his narrative were bought up in one year.
In 1763 the French government sent out a similar expedition under Louis Antoine de Bougainville, with instructions to establish a French settlement in the Falkland Islands; their position three hundred miles east of the Strait of Magellan gave them military value for control of the passage from the Atlantic to the Pacific. He accomplished his mission and returned to France. In 1765 he sailed again, passed through the strait into the Pacific, reached Tahiti (1768)—which Samuel Wallis had discovered a year before—took possession of it for France, discovered the Samoa group and the New Hebrides Islands, rounded the Cape of Good Hope, and reached France in 1769, bringing from the Pacific tropics the bougainvillaea vine. His account of his voyage stressed the pleasant climate of Tahiti and the happy health, good nature, and easy morals of the natives. We shall find Diderot commenting enviously on this report in his Supplément au Voyage de Bougainville.
In 1764 the British government commissioned Captain John Byron to pick up some useful territory in the South Seas. He landed at Fort Egmont in the Falkland Islands and took possession of the islands for England, not knowing that the French were already there. Spain claimed prior possession, France yielded to her, Spain yielded to England (1771), Argentina claims them today. Byron continued around the globe, but left no further mark on history. In an earlier voyage, as midshipman under Anson, he had been shipwrecked on the Chile coast (1741); his account of this was used by his grandson Lord Byron in Don Juan.
For English-speaking peoples the outstanding explorer of the eighteenth century was Captain James Cook. Son of a farm laborer, he was apprenticed at twelve to a haberdasher. Finding insufficient adventure in lingerie, he joined the navy, served as “marine surveyor” along the coasts of Newfoundland and Labrador, and acquired a reputation as mathematician, astronomer, and navigator. In 1768, aged forty, he was chosen to lead an expedition for noting the transit of Venus, and making geographical researches, in the South Pacific. He sailed August 25 on the Endeavour, accompanied by several scientists, one of whom, Sir Joseph Banks, had equipped the vessel out of his own funds.X The transit was observed at Tahiti June 3, 1769. Thence Cook sailed in quest of a great continent (Terra Australis) supposed by some geographers to be hiding in the southern seas. He found none, but he explored the Society Islands and the coasts of New Zealand, charting them carefully. He went on to Australia (then known as New Holland), took possession of the eastern coast for Great Britain, sailed around Africa, and reached England on June 12, 1771.
On July 13, 1772, with the Resolution and the Endeavour, he set out again to find the imaginary southern continent. He searched the sea eastward and southward between the Cape of Good Hope and New Zealand, and crossed the Antarctic Circle to 71° south latitude without seeing land; then the mounting danger from ice floes compelled him to turn back. He visited Easter Island, and wrote a description of its gigantic statues. He charted the Marquesas and Tonga Islands, and called the latter “Friendly” because of the gentleness of the natives. He discovered New Caledonia, Norfolk Island, and the Isle of Pines (Kunie). He traversed the South Pacific eastward to Cape Horn, continued over the South Atlantic to the Cape of Good Hope, sailed north to England, and reached port July 25, 1775, after a voyage of over sixty thousand miles and 1,107 days.
His third expedition sought a water route from Alaska across North America to the Atlantic. He left Plymouth July 12, 1776, with the Resolution and the Discovery, sailed around the Cape of Good Hope, touched again at Tahiti, proceeded northeast, and chanced upon his greatest discovery, the Hawaiian Islands (February, 1778). These had been seen by the Spanish navigator Juan Gaetano in 1555, but they had been forgotten by Europe for over two centuries. After continuing northeast, Cook reached what is now the state of Oregon, and surveyed the North American coast up to and beyond Bering Strait to the northern limits of Alaska. At 70° 41’ north latitude his advance was barred by a wall of ice rising twelve feet above the sea and stretching as far as the crow’s-nest eye could reach. Defeated in his search for a Northeast Passage across America, Cook returned to Hawaii. There, where previously he had received a friendly welcome, he met his end. The natives were kind but thievish; they stole one of the Discovery’s boats; Cook led a group of his men to recapture it; they succeeded, but Cook, who insisted on being the last to leave the shore, was surrounded by the angry natives, and was beaten to death (February 14, 1779), aged fifty-one. England honors him as the greatest and noblest of her maritime explorers, an accomplished scientist, a fearless captain loved by all his crews.
Almost as heroic was the expedition led by Jean François de Galaup, Comte de La Pérouse, commissioned by the French government to follow up Cook’s discoveries. He sailed in 1785 around South America and up to Alaska, crossed to Asia, and was the first European to pass through the strait (which till lately bore his name) between Russian Sakhalin and Japanese Hokkaido. Turning south, he explored the coast of Australia and reached the Santa Cruz Islands. There, apparently, he was shipwrecked (1788), for he was never heard of again.
Land exploration was also a challenge to the lust for adventure and gain. In 1716 a Jesuit missionary reached Lhasa, the “Forbidden City” of Tibet. Carsten Niebuhr explored and described Arabia, Palestine, Syria, Asia Minor, and Persia (1761). James Bruce traveled through East Africa and rediscovered the source of the Blue Nile (1768). In North America French explorers founded New Orleans (1718) and moved north along the Mississippi to the Missouri; in Canada they struggled to reach the Pacific, but the Rocky Mountains proved insurmountable. Meanwhile English settlers pushed inland to the Ohio River, and Spanish friars led the way from Mexico through California to Monterey, and up the Colorado River basin into Utah; soon North America would be one of the prizes in the Seven Years’ War. In South America La Condamine, after measuring a degree of latitude at the equator, led an expedition from the sources of the Amazon near Quito to its mouth at the Atlantic, four thousand miles away.
The mapmakers could never quite keep up with the explorers. Through half a century (1744–93) César François Cassini and his son Jacques Dominique issued in 184 successive sheets a map of France thirty-six feet long by thirty-six feet wide, showing in unprecedented detail all roads, rivers, abbeys, farms, mills, even wayside crosses and gallows. Torbern Olof Bergman, not content with being one of the greatest chemists of the eighteenth century, published in 1766 a Werlds Beskribning, or world description,summarizing the meteorology, geology, and physical geography of his time. He suggested that many islands were peaks of mountain ranges now mostly submerged; so the West Indies might be the remains of a range that had connected Florida with South America. Horace de Saussure, after twenty-four years as professor of philosophy at the University of Geneva, made famous ascents of Mont Blanc (1787) and the Klein Matterhorn (1792), and composed voluminous studies of Swiss mountains in their atmospheric conditions, formations, strata, fossils, and plants, making a marvelous mixture of meteorology, geology, geography, and botany. Let us remember, when we are told that history is the Newgate Calendar of nations, that it is also the record of a thousand forms of heroism and nobility.