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THE POPULAR SCIENCE MONTHLY. 



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 exca- 

 vated by the volume of water now flowing 

 at ordinary stages. In fact, there seems 

 little doubt that tho 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 dis- 

 covery, at that depth below the present sur- 

 face 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 Val- 

 ley 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 north- 

 ward to Ilamilton; there they turned to the 

 west and south, and reached the Ohio River 

 Valley as it is now, somewhere near Law- 

 renceburg, 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 com- 

 pletely 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 debris of the retired ice-field, 

 and finding, perhaps, that the former im- 

 passable 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 & 



lecture delivered at the Franklin Institute, 

 December 18, 1886, by Mr. Charles A. Ash- 

 burner, Geologist in charge of the State Geo- 

 logical 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 arc in the city proper. 

 The total area of pipe leading into Pitts- 

 burg is given as 1,346,608 square inches, 

 and the total capacity of the mines is esti- 

 mated 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 pur- 

 poses 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 con- 

 sumer 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 



