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424 new courses only in places here and there. The Ohio River seems to have been in the latter category, for in many places its valley is too wide and too deep to have been excavated by the volume of water now flowing at ordinary stages. In fact, there seems little doubt that the Ohio flows in a channel which was cut long previous to the glacial period. This old channel has been largely filled up, and the river now flows from thirty-five to forty feet above its ancient bed. This seems to be proved by the discovery, at that depth below the present surface of the ground, of an extensive bed of carbonaceous material consisting of stumps of trees, leaves, seeds, and other vegetable remains. Several facts seem to point to the conclusion that on and near the site of the city was once spread out a sheet of water that assumed almost the aspect of a lake. The outlet of this sheet was not like the present course of the river, past the mouth of Mill Creek, but up what is now Mill Creek Valley on one side, and up the Little Miami Valley and an ancient channel between Red Bank and Plainville on the other side, of what then formed an island now occupied by a part of the hill suburbs of Cincinnati. These ancient channels extended northward on the east and west of the island, and united near where Ludlow Grove now is, and thence together held their way northward to Hamilton; there they turned to the west and south, and reached the Ohio River Valley as it is now, somewhere near Lawrenceburg, Indiana, by following the course now used by the Big Miami. In those days a barrier of land stretched from Price Hill across to the Kentucky side. It is supposed that during the glacial period the end of an immense glacier extended south as far as the Ohio River, and at Cincinnati so completely blocked the channel as to compel the river to seek another course. But at the close of the ice age, and when the glacier had melted, the river attempted to return to its former channels. Finding, however, its old bed filled with sand and gravel, the débris of the retired ice-field, and finding, perhaps, that the former impassable barrier had lost some of its height, it beat against it, gradually wore it away, and cut for itself a new channel from the mouth of Mill Creek to Lawrenceburg.

Natural Gas at Pittsburg.—From a lecture delivered at the Franklin Institute, December 18, 1886, by Mr. Charles A. Ashburner, Geologist in charge of the State Geological Survey, it appears that there are now six natural gas companies in Pittsburg, managing 107 wells, and supplying the gas through more than 500 miles of pipe, of which 232 miles are in the city proper. The total area of pipe leading into Pittsburg is given as 1,346,608 square inches, and the total capacity of the mines is estimated at more than 250,000,000 cubic feet of gas per day. One company supplies more than 400 manufactories and 7,000 dwellings with all the fuel consumed in them. The composition of the gas varies greatly, but it may be generally described as a mixture of hydrogen, nitrogen, and marsh gas, with occasionally higher carbon compounds. A thousand cubic feet of gas is calculated to equal in heating capacity fifty-five pounds of coal. The use of gas for domestic purposes has been facilitated by the inventions of Mr. Westinghouse, among which are a device for preventing leaks and a pressure-regulator. The gas is furnished to the consumer on a yearly contract with a company for supply at certain rates and costs, to heat and light a house containing twelve rooms for from $70 to $90 a year. With it, every room may be kept at a temperature not varying two degrees, regardless of the condition of the outside temperature, or of pressure on the mains. While the lecturer admitted that the source of natural gas is capable of exhaustion, he did not think there was any imminent danger of such a calamity.

Origin of the "Second Growth" in Woods.—The origin of the second growth that springs up after a forest has been cleared away, which is usually different in kind from the previous growth, has given rise to one of the problems that have never been solved. Perhaps the most frequently suggested explanation is that it springs up from seeds that have lain dormant in the ground for centuries; but aside from its being hard to conceive of seeds preserving their vitality for so long a time under the conditions to which they must be exposed, this supposition does not account for the