and Prof. George H. Williams, of Baltimore, vice-presidents; and Prof. H. L. Fairchild, of Rochester, N. Y., secretary. About sixty papers were presented at this meeting, a few of which are here briefly noticed:
In his address as the retiring president, Sir J. William Dawson, of Montreal, chose for his subject Some Recent Discussions in Geology, considering especially the building up and development of the continents. He noted the controversies respecting the age of the older crystalline rocks, the true foundation stones of continents, instancing those of the Highlands of Scotland as described by Geikie, and the older rocks of North America as worked out by Logan and his successors. He was inclined to think that the oldest rocks that we shall know are the gneisses of the lower Laurentian, and that these may be regarded as the igneo-aqueous products of the earliest action of the waters on the crust of a cooling globe. He then referred to the rival theories of mountain-building, and, after distinguishing between mountains of eruption (volcanoes), like Vesuvius and Cotopaxi, mountains of slightly inclined strata, like the Lebanon and the Sierra Nevada, and mountains of contorted strata, like the Alps and the Appalachians, noted the diverse views as to the origin of the latter. He favored the time-honored contraction theory as explained recently by Le Conte, but saw no objection to connecting with this the deposition theory of Hall and others, the expansion theory of Mellard Reade, and the isostatic theory of Dutton. When it is necessary to account for the compression of vast masses of rock into a third of their normal dimensions and for their elevation thousands of feet above the level of the sea, we may be thankful to invoke all available powers each in its proper place, and the sculpturing due to atmospheric agencies besides.
Prof. C. H. Hitchcock, of Hanover, N. H., spoke about Ancient Eruptive Rocks in the White Mountains. He said that in his reports of the New Hampshire Geological Survey he had described in detail a great variety of granites occurring in the White Mountains, without having discovered the principle of their association. He then reviewed the order of these varied igneous rocks and showed that the same structure found in volcanoes appeared in the White Mountains. He was therefore convinced that the granites were truly eruptive. If the modern view of the formation of granite is correct, the depth at which it is formed, as shown in the White Mountain region, is from two thousand to five thousand feet, and decidedly not forty thousand feet, as some geologists have maintained.
Prof. George H. Williams, of Johns Hopkins University, treated the subject of Ancient Volcanic Rocks along the Eastern Border of North America. He proposed to designate as volcanic only such igneous rocks as had flowed up through vents to the surface. All existing knowledge of the occurrence of these rocks during the early geologic ages in eastern North America was summarized, beginning with Newfoundland and passing southwestward along the Appalachian mountain belt.
Mr. Alexander Agassiz, Director of the Museum of Comparative Zoölogy at Harvard University, presented An Account of an Expedition to the Bahamas, which were described as formed of wave-worn and windblown coral sands.
Among the papers relating to the glacial drift, Prof. T. C. Chamberlin and Mr. Frank Leverett discussed Certain Features of the Past Drainage Systems of the Upper Ohio Basin, concluding that the lower portions of the rock valleys of the upper Ohio and its tributaries were eroded during an interglacial epoch. Prof. G. Frederick Wright, describing parts of the same region in a paper on the Glacial History of Western Pennsylvania, referred the valley erosion in rock almost wholly to a preglacial time of higher altitude of the country, citing the occurrence of glacial gravel deposits extending from the high terraces down to the bottom lands, and regarding the Ice age as continuous and geologically short.
The Harvard Observatory.—The beginning of the Astronomical Observatory of Harvard College is usually identified with the appointment of Prof. W. C. Bond as observer in 1840. The appearance of the first comet of 1843 excited fresh interest in the subject, and funds were collected to buy the great telescope, which then had only one match in the world, in 1847. The resources of the observatory have since been increased by various subscriptions, gifts, and bequests. The
