Aprils, 1877] 



NATURE 



487 



leagues have satisfied themselves that during the depo- 

 sition of the Upper Carboniferous or Productive Coal- 

 measures, the Cincinnati land formed a barrier between 

 the marshes of Ohio and Indiana ; in other words, that 

 the Alleghany and Illinois Coal-fields were never united, 

 at least as far south as Alabama and Arkansas, where 

 wide-spread tertiary deposits obscure all evidence bearing 

 on the point. 



" It is important," says Prof. Orton, " to mark the 

 following fact distinctly, viz., that there is quite a broad 

 tract at the summit of the fold in which the beds have 

 but little dip. It is hard to speak of an axis without 

 involving the idea of a line, but there is probably no part 

 of this region of less than a score of miles that deserves, 

 by way of excellence, the name of the Cincinnati axis. 

 In other words, this fold has a broad and flat axis, rather 

 than a linear one." The elevation has been so gentle and 

 so gradual that direct visible evidence of unconformable 

 succession is hardly to be expected. 



No reader will fail to be struck by the important place 

 accorded to chemical geology in the Reports. This por- 

 tion of the work has been done mainly by Prof. Wormley, 

 and adds greatly to the value of the survey as a whole. 

 He has not confined his investigations to minerals of im- 

 mediate economic importance, but has placed on record 

 many analyses that must for a long time to come be 

 drawn upon with advantage as the development of the 

 resources of the State goes on. Especially as regards 

 limestones and cement-stones and the amount of sulphur 

 in the various coal-seams, very complete and useful infor- 

 mation is given. 



More than a score of counties " lie wholly within the 

 limits of the productive coal-measures," and of nearly as 

 many the geological surveyors pronounce without hesi- 

 tation that " the soil will necessarily always be the source 

 of their greatest material wealth." It sounds strange to 

 hear already from such a rich agricultural district as 

 Western Ohio the cry of exhaustion of the soil, but as all 

 the surveyors without exception sound the note of warning 

 against unskilful farming, it is evident that ere long 

 science will have to be called in to assist nature if the 

 productiveness of the State is to be maintained. 



Although doubtless to be discussed more fully in the 

 volume on economic geology, the coal and ironstone 

 seams of the great coal-field, and the salt, oil, and gas 

 industries receive much attention in the various county 

 Reports. Prof. E. B. Andrews furnishes a chapter on 

 coal which is full of interesting facts. Mr. M. C. Read gives 

 a plan of a coal-mine in Trumbull County, which shows 

 how very local was the formation of the seam. The coal 

 thins out on every side, and presents the outline of a long 

 winding swamp with branching creeks. 



The importance of the ironstone beds in Ohio is well 

 known. A black- band in Tuscarawas County locally 

 attains, according to Prof. Newberry, a thickness of 

 12 feet. 



The excitement caused by the discovery of the oil-wells 

 of Pennsylvania and Ohio will yet be fresh in the me- 

 mory of our readers. The conditions under which petro- 

 leum occurs are well illustrated in the Reports. There 

 must be a mass of carbonaceous shales from whose 

 organic contents the hydro-carbons are slowly distilled, 

 and an overlying porous rock for the storage of the pro- 



ducts — best of all a jointed sandstone with an imper- 

 vious stratum for a roof— if dome-shaped so much the 

 better. When these conditions are present the oil is 

 ready for the fortunate landowner, and his luck is the 

 greater if he happen to strike a joint where a quantity 

 can collect. So well is this now understood that when a 

 well shows symptoms of giving out, a torpedo is exploded 

 in it to loosen up the rock and open out the way to 

 neighbouring fissures. Carbonaceous shales, yielding oil, 

 are met with at various horizons from the Huron (Devo- 

 nian) upwards. 



Carburetted hydrogen gas occurs under similar con- 

 ditions and is now expressly bored for. The town of 

 Fredonia, N.Y., has been lighted up with natural gas for 

 more than forty years. In Knox County, Ohio, two wells 

 were sunk to the Huron shale. " At a depth of about 

 600 feet, in each well, a fissure was struck from which gas 

 issued in such volume as to throw out the boring tools 

 and form a jet of water more than 100 feet in height. . . 

 One of these wells constantly ejects, at intervals of one 

 minute, the water that fills it. It thus forms an inter- 

 mittent fountain 120 feet in height. The derrick set 

 over this well has a height of 60 feet. In winter it 

 becomes encased in ice, and forms a huge translucent 

 chimney, through which, at regular intervals of one 

 minute, a mingled current of gas and water rushes to 

 twice its height. By cutting through this hollow cylinder 

 at its base and igniting the gas in a paroxysm, it affords 

 a magnificent spectacle, a fountain of mingled water and 

 fire which brilliantly illuminates the icy chimney. No 

 accurate measurement has b een made of the gas escaping 

 from these wells, but it is estimated to be sufficient to 

 light a large city." Unfortunately there is no large city 

 to light. 



Geologists had a right to expect from Ohio an important 

 contribution to their knowledge of the Glacial period, and 

 Prof. Newberry and his colleagues have not disappointed 

 them. The chief geologist sums up the results of the 

 Survey in a masterly essay, and it is satisfactory to find 

 that his views to a great extent corroborate the conclu- 

 sions at which glacialists in Europe have arrived. Want 

 of space compels us to allude to these in the briefest 

 manner. The cold came on at a period when the land 

 stood considerably higher than at present, as is proved 

 by numerous river channels deeply buried beneath the 

 drift. A wide-spread boulder clay or hard-pan, the pro- 

 duct of a land ice-sheet radiating from the Canadian 

 Mountains marks an early, and the greatest, development 

 of the cold. A subsidence followed on the retreat of the 

 ice-sheet, and a stratified clay was deposited over low- 

 lying portions of the hard-pan. Then a forest covered a 

 large portion of the glacial deh'is, and this furnishes 

 remains of the mammoth, mastodon, and giant beaver. 

 Another submergence covered the forest-bed with the 

 loess of the Mississippi Valley, and icebergs strewed 

 boulders from Canada over the State. Much of the older 

 drift was reasserted and heaped up into kaims or eskars. 

 Lastly, the sea gradually retired, occasionally pausing, 

 and giving rise to terraces in the river valleys. 



Intimately connected with the Glacial period were the 

 hollowing out of the great lake-basins, and numerous im- 

 portant changes in the drainage-system of the continent. 

 Taking Lake Erie as the simplest case, it is clear that its 



