ESTIMATING THE AGE OF NIAGARA FALLS. 151 



not 

 accompany- 



mile of the face of the wall where it is a hundred and fifty feet 

 high, the whole amount of enlargement of the mouth of the gorge 

 would be accomplished in less than ten thousand years. Exact ac- 

 counts have not been kept by the railroad; but even a hasty exami- 

 nation of the face of the wall makes it sure that the actual amount 

 removed has been greatly in excess of six hundred yards annually. 

 This estimate is based partly on the impression of the railroad officials 

 as to the cost of re- 

 moval, and partly on 

 the impressions of the 

 watchmen who spend 

 their time in keeping- 

 guard and in the work 

 of removing it. 



But that is 

 all. The 



ing photogravures indi- 

 cate an actual amount 

 of removal over a part 

 of the area enormously 

 in excess of the rate 

 supposed. Fig. 5 shows 

 a portion of the preci- 

 pice, a hundred feet 

 high, where the road 

 first comes down to the 

 level of the Clinton 

 limestone, and where, 

 consequently, the 

 whole thickness of the 

 Niagara shale is acces- 

 sible to examination. Fortunately, Patrick MacNamara, the watch- 

 man at this station, was a workman on the road at the time of its 

 construction in 1854, and has been connected with the road ever 

 since, having been at his present post for twelve years. We have 

 therefore his distinct remembrance, as well as the appearance of 

 the bank, to inform us where the face of the original excavation 

 then was. In the picture he is standing at the original face, while 

 the other figure is nearly at the back of the space which has been 

 left empty by the crumbling away of the shale. The horizon- 

 tal distance is fully twenty feet, and the rocks overhang to that 

 amount for the whole distance exposed in the photograph. All this 

 amount of shale has fallen down in forty-four years, making a rate 

 many times larger than the highest we have taken as the basis of our 



FIG. 4. Nearer view of the upper portion of the face near 

 the mouth, showing the exposure of the situation ai 

 that point. 



