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574 that this, including the calculus and differential equations, can not be safely neglected by the engineer—though some of the more abstruse portions of the subject might be dispensed with. Physics is of great importance, for there are few problems in engineering in which no part is borne by physical considerations. The surveyor avails himself of physics when heights are measured by the barometer, or by the temperature at which water boils. Evaporation, condensation, and latent heat bear upon the efficiency of steam engines, and the expansive force of gases, the retention of the heat developed, and the diminution of friction on the economical working of heat engines. Considerations of temperature limit the height to which railways can be carried without danger of blocking by snow, and the depth at which tunnels can be driven. Compressed air is largely used by engineers. Electric engineering, too, is intimately connected with physics. Chemistry is of importance in the manufacture of iron, steel, and other metals, and the formation of alloys, and in its relation to explosives. A knowledge of geology is indispensable in directing a search for coal, iron ore, and the metals, and in the execution of all works going below the surface. Meteorology is useful to the engineer in that it enables him to know the force of the wind and the direction, duration, and periods of occurrence of severe gales—very important matters in the construction of bridges and harbor works,

A Valley of White Limestone.—A remarkable formation is described by Mr. Theodore Bent as observed by him while exploring the frankincense country of Arabia, near the presumed site of the Abyssapolis of Ptolemy. The valley leading down to the Red Sea has been filled in the course of ages by a calcareous deposit, which is collected on either side of an isolated hill in the middle of the hollow, about one thousand feet in height. This deposit has taken the form of a straight and precipitous wall five hundred and fifty feet high and three quarters of a mile long on the eastern side of the bill, and about a quarter of a mile long and three hundred feet high on the western side. Over these walls feathery waterfalls precipitate themselves, adding perpetually to the chalky accretions of which the cliffs are constructed. The general appearance of the walls is white and whitish-gray, with long, white stalactites hanging down in tumbled confusion. They are streaked here and there, where the water perpetually falls, with patches of green. Beneath plateaus twenty feet high enormous ricinuses, daturas, and other plants flourish; and the Bedouins have utilized the stream before it has lost itself in the rocky channel to make small gardens. The rocky channel below is also very curious, presenting a flat surface about fifty yards across of white calcareous rocks, while just below the wall where the water comes down is an enormous amount of white calcareous deposit, soft and spongy to walk upon. Mr. Bent pronounces this one of the most stupendous natural phenomena he has ever seen, characterizes the valley as "a stupendous abyss," and compares the whole with the pink and white terraces of New Zealand and the calcareous deposits of Yellowstone Park.

Geology and Paleontology at Union University.—The department of Geology and Paleontology of Union University offers the ordinary course of the college and special courses for such students as are interested in the science from a philosophical or professional point of view. The courses include mineralogy and lithology, general geology (with excursions), economic geology, in which are considered in the second half the occurrence and distribution of the mineral deposits and building stones of the United States; systematic and structural geology and paleontology, with especial consideration of the formations occurring in New York and adjacent States and their characteristic fossils; field and laboratory study of the geological formations readily accessible from Schenectady; the methods of preparing geological maps and reports; and advanced field work and independent research, in which the student selects some region for original work to which he can devote considerable time, and conducts his investigation in a professional manner. He is expected in this to demonstrate his ability to conduct original work, and to prepare a report containing a summary of the previous knowledge of the geology of the region, with