PREFACE
In no department of science is the slow and chequered progress of investigation more conspicuous than in that branch of Geology which treats of volcanoes. Although from the earliest dawn of history, men had been familiar with the stupendous events of volcanic eruptions, they were singularly slow in recognizing these phenomena as definite and important parts of the natural history of the earth. Even within the present century, the dominant geological school in Europe taught that volcanoes were mere accidents, due to the combustion of subterranean beds of coal casually set on fire by lightning, or by the decomposition of pyrites. Burning mountains, as they were called, were believed to be only local and fortuitous appearances, depending on the position of the coal-fields, and having no essential connection with the internal structure and past condition of our planet. So long as such fantastic conceptions prevailed, it was impossible that any solid progress could be made in this branch of science. A juster appreciation of the nature of the earth's interior was needed before men could recognize that volcanic action had once been vigorous and prolonged in many countries, where no remains of volcanoes can now be seen.
To France, which has led the way in so many departments of human inquiry, belongs the merit of having laid the foundations of the systematic study of ancient volcanoes. Her groups of Puys furnished the earliest inspiration in this subject, and have ever since been classic ground to which the geological pilgrim has made his way from all parts of the world. As far back as the year 1752, Guettard recognised that these marvellous hills were volcanic cones that had poured forth streams of lava. But it was reserved for Desmarest twelve years later to examine the question in detail, and to establish the investigation of former volcanic action upon a broad and firm basis of careful observation and sagacious inference. His method of research was as well conceived as the region of Auvergne was admirably fitted to be the field of exploration. He soon discovered that the volcanoes of Central France were not all of one age, but had made their appearance in a long series, whereof the individual members became less perfect and distinct in proportion to their antiquity. Beginning with the cones, craters, and lava-streams which stand out so fresh that they might almost be supposed to have been erupted only a few generations ago, Desmarest traced the volcanic series backward in time, through successive stages of the decay and degradation wrought upon them by the influence of the atmosphere, rain and running water. He was thus able, as it were, to watch the gradual obliteration of the cones, the removal of the ashes and scoriæ, and the erosion of the lava-streams, until he could point to mere isolated remnants of lava, perched upon the hills, and overlooking the valleys which had been excavated through them. He showed how every step in this process of denudation could be illustrated by examples of its occurrence in Auvergne, and how, in this way, the various eruptions could be grouped according to their place in the chronological sequence. To this illustrious Frenchman geology is thus indebted, not only for the foundation of the scientific study of former volcanic action, but for the first carefully worked out example of the potency of subærial erosion in the excavation of valleys and the transformation of the scenery of the land.
While these fruitful researches were in progress in France, others of hardly less moment were advancing in Scotland. There likewise Nature had provided ample material to arrest the attention of all who cared to make themselves acquainted with the past history of our globe. Hutton, as a part of his immortal Theory of the Earth, had conceived the idea that much molten material had been injected from below into the terrestrial crust, and he had found many proofs of such intrusion among the rocks alike of the Lowlands and Highlands of his native country. His observations, confirmed and extended by Playfair and Hall, and subsequently by Macculloch, opened up the investigation of the subterranean phases of ancient volcanic action.
Under the influence of these great pioneers, volcanic geology would have made steady and perhaps rapid progress in the later decades of last century, and the earlier years of the present, but for the theoretical views unfortunately adopted by Werner. That illustrious teacher, to whom volcanoes seemed to be a blot on the system of nature which he had devised, did all in his power to depreciate their importance. Adopting the old and absurd notion that they were caused by the combustion of coal under ground, he laboured to show that they were mere modern accidents, and had no connection with his universal formations. He proclaimed, as an obvious axiom in science, that the basalts, so widely spread over Central and Western Europe, and which the observations of Desmarest had shown to mark the sites of old volcanoes, were really chemical precipitates from a primeval universal ocean. Yet he had actually before him in Saxony examples of basalt hills which entirely disprove his assertions.
Fortunately for the progress of natural knowledge, Werner disliked the manual labour of penmanship. Consequently he wrote little. But his wide range of acquirement, not in mineralogy only, his precision of statement, his absolute certainty about the truth of his own opinions, and his hardly disguised contempt for opinions that differed from them, combined with his enthusiasm, eloquence and personal charm, fired his pupils with emulation of his zeal and turned them into veritable propagandists. Misled as to the structure of the country in which their master taught, and undisciplined to investigate nature with an impartial mind, they travelled into other lands for the purpose of applying there the artificial system which they had learnt at Freiberg. The methodical but cumbrous terminology in which Werner had trained them was translated by them into their own languages, where it looked still more uncouth than in its native German. Besides imbibing their teacher's system, they acquired and even improved upon his somewhat disdainful manner towards all conclusions different from those of the Saxon Mining School.
Such was the spirit in which the pupils of Werner proceeded to set the "geognosy" of Europe to rights. The views, announced by Desmarest, that various rocks, far removed from any active volcano, were yet of volcanic origin, had been slowly gaining ground when the militant students from Saxony spread themselves over the Continent. These views, however, being irreconcilable with the tenets enunciated from the Freiberg Chair, were now either ignored or contemptuously rejected. Werner's disciples loved to call themselves by their teacher's term "geognosts," and claimed that they confined themselves to the strict investigation of fact with regard to the structure of the earth, in apparent unconsciousness that their terminology and methods were founded on baseless assumptions and almost puerile hypotheses.
With such elements ready for controversy, it was no wonder that before long a battle arose over the origin of basalt and the part played by volcanoes in the past history of the globe. The disciples of Werner, champions of a universal ocean and the deposition of everything from water, were dubbed Neptunists, while their opponents, equally stubborn in defence of the potency of volcanic fire, were known as Vulcanists or Plutonists. For more than a generation this futile warfare was waged with extraordinary bitterness—dogmatism and authority doing their best to stop the progress of impartial observation and honest opinion.
One of the most notable incidents in the campaign is to be found in the way in which the tide of battle was at last turned against the Wernerians. Cuvier tells us that when some of the ardent upholders of the Freiberg faith came to consult Desmarest, the old man, who took no part in the fray, would only answer, "Go and see." He felt that in his memoir and maps he had demonstrated the truth of his conclusions, and that an unprejudiced observer had only to visit Auvergne to be convinced.
By a curious irony of fate it was from that very Auvergne that the light broke which finally chased away the Wernerian darkness, and it was by two of Werner's most distinguished disciples that the reaction was begun.