as the most outstanding feature in them was intrusions of rock which were supposed to have come up to the surface of the earth molten with the heat of the nether regions, over which Pluto was supposed to reign. The rival theories were debated with great heat and incredible bitterness. The Neptunists, because their primordial ocean, in which the rocks were formed, seemed to have some connection with the Noachian deluge, were judged to be on the side of righteousness, whereas the Plutonists, although they were able to show ample evidence for their views, were looked upon as followers of Antichrist, because their theories ran counter to the Book of Genesis. Time has softened the bitterness, but has not removed all traces of the quarrel. The Plutonists won the day, and still hold the upper hand, but it is becoming apparent that the central heat from which they derived their molten rocks is a myth, and Werner's solution theory of crystalline rocks is not only a tenable theory, but one more in accordance with physical laws. This century-old controversy is typical of geological work at the present day; the evidence appeals to different people in different ways, and each view contains some portion of the truth. The elements of all geological problems are so complex that dogmatic assertion can find no place in the science. Geology teaches one to weigh evidence and to arrive at conclusions which must be based on wide knowledge and logical reasoning for them to have any value. The beginner misses the artificial aids to knowledge rendered in other sciences by measurements and numerical estimates, and the predominant note at first may appear to be given by the mass of apparently vague and conflicting data. After a. while, however, the main issues of the science become clear
