NIAGARA AS A TIMEPIECE. 



shown on the map of the gorge (Fig. 9), and in the longitudinal section 

 in Fig. 16. 



The Whirlpool and its Ravine. — The elbow of the Niagara 

 gorge at the whirlpool 

 has given rise to much 

 speculation and has 

 led to great confusion. 

 Fifty years ago. Sir 

 Charles Lyell sup- 

 posed that it indicated 

 an ancient course of 

 the river itself, which 

 extended thence to 

 the St. Davids' Val- 

 ley, about four or 

 five miles distant, al- 

 though the country 

 forms a level floor 

 which told of no bur- 

 ied channel (see Fig. 

 5). This mistake arose 

 from the perpendicu- 

 lar walls of the whirl- 

 pool basin, without the 

 necessity of sloping 

 sides for ancient val- 

 leys being then per- 

 fectly known, and 

 without the author evi- 

 dently going through 

 the ravine where rocks 

 were exposed. The se- 

 rious feature of the 

 mistake was that it led 

 to the supposition that 

 perhaps much of the 

 gorge above the whirl- 

 pool was older than 

 that portion below, 

 and, becoming filled 

 with drift, the river 

 had only the drift fill- 

 ing to remove in mod- 

 ern times. This idea 

 caused Dr. Pohlman to reduce the age of the falls to three thou- 

 sand years. But almost universally the error of a deep preglacial 



GARA 



Fig. 9. — Map of the Niagara Gorge (United States Lake 

 Survey), showing its Variable Width and Cross- 

 sections. 



