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SCIENCE. 



[N. S. Vol. VIII. No. 198. 



a corresponding terrace just outside the 

 mouth of the gorge ; and these terraces, 

 with other parts of the shore line in the 

 Ontario basin which marks the rise of the 

 waters so as to fiood the Niagara gorge, are 

 here named the Niagara strand. The rising 

 of the waters was occasioned by the lifting 

 of the barrier at the outlet of Lake Ontario 

 to an elevation 100 feet higher than now. 

 By the subsequent erosion of this barrier, 

 which was partly composed of drift, the 

 actual fall of the Niagara waters has been 

 increased to its present figure. The reduc- 

 tion of the descent of the river is found to 

 be sufScient to account for the shallowness 

 of the channel at the Whirlpool rapids. 

 The narrowing of this section is explained 

 by the fact that the youthful Niagara took 

 possession of a small preglacial valley there, 

 giving greater depth to the river. It is 

 further probable that the volume of the 

 river was less at that time, since it is sup- 

 posed that a portion of the outflow of the 

 Great Lakes then passed to the Mississippi. 

 15. The Age of Niagara Falls as Indicated 

 by the Erosion at the Mouth of the Gorge. By 

 Professor G. Frederick Wright, Oberlin, 

 Ohio. The late Dr. James Hall early noted 

 the significant fact that " the outlet of the 

 chasm below Niagara Falls is scarcely 

 wider than elsewhere along its course." 

 Clearly this is important evidence of the 

 late date of its origin, and it has been used 

 by the author and others in support of the 

 short estimates which have been made con- 

 cerning the length of time separating us 

 from the Glacial period. A close examina- 

 tion made by the author this summer 

 greatly strengthens the force of the argu- 

 ment, since he found that the disintegrating 

 forces tending to enlarge the outlet and 

 give it a V-shape are more rapid than has 

 been supposed. The depth of the gorge at 

 the outlet, from the top of the Niagara 

 limestone to the river, is 340 feet. The 

 thickness of that formation of limestone at 



the surface is here, however, only about 40 

 feet ; while the soft Niagara shales under- 

 lying it are from 60 to 75 feet thick. Be- 

 low there is a stratum of Clinton limestone 

 30 feet in thickness, and below that a shaly 

 deposit of 70 feet. The Niagara shales at 

 this point have never been covered by 

 talus, so that they have always been ac- 

 cessible to disintegration by atmospheric 

 agencies. 



Somewhat over forty years ago a railroad 

 was built along the face of the eastern side 

 of the gorge, affording an opportunity to 

 observe the rate of disintegration. All 

 along where a perpendicular exposure was 

 made, the shale has crumbled away to an 

 extent of several feet, and in some places to 

 that of 20 feet. A conservative estimate 

 of the rate of disintegration for the 70 feet 

 of Niagara shales supporting the Niagara 

 limestone would be one inch a year, with a 

 probable rate of two inches a year. But at 

 the lowest estimate no more than 12,000 

 years would be required for the enlarge- 

 ment of the upper part of the mouth of the 

 gorge 1,000 feet on each side, which is very 

 largely in excess of the actual amount of 

 enlargement. Some of the recent esti- 

 mates, therefore, which would make the 

 gorge from 30,000 to 40,000 years old, are 

 evidently extravagant, and must incorpo- 

 rate some error in their premises. The age 

 of the gorge cannot be much more than 10- 

 000 years, and is probably considerably less, 



16. A Recently Discovered Cave of Celestite 

 Crystals at Put-in-Bay, Ohio. By Professor 

 G. Frederick Wright. The principal lo- 

 cality in America from which museums 

 have been supplied with specimens of celes- 

 tite (sulphate of strontium) is Strontian 

 Island, two or three miles from Put-in-Bay 

 Island, in the western end of lake Erie. 

 Just as this supply was becoming-exhausted, 

 a remarkable fissure was discovered last 

 winter on Put-in-Bay Island, which is com- 

 pletely surrounded with very large crystals 



