November 27, 1908] 



SCIENCE 



755 



somewhere said — when controversy ceases the 

 interest passes away, and the truth generally 

 lies between the extremes. The value of the 

 points raised must he taken in their magni- 

 tude relative to what has already been estab- 

 lished in the investigations of Niagara Falls; 

 accordingly, a backward sketch of some of the 

 results must be made. 



Tears ago Dr. Gilbert presented data, in 

 mathematical form, demonstrating that the 

 Falls were no more than 7,000 years old, with 

 several modifications tending to lower even 

 this estimate (page 372). Shortly afterwards, 

 my discovery that the Huron discharge had 

 formerly nothing whatever to do with Lake 

 Erie, or the Niagara (page 294, also Chap. 

 XXV., and Ap. VII.), changed the then new 

 idea of the short age of Niagara Falls. This 

 now universally accepted fact is further 

 proved by new soundings (pp. 71, 73), within 

 and without the end of the gorge, bringing to 

 light a narrow deep inner channel that could 

 carry only the Erie drainage. The same phe- 

 nomena I also found in the expanded reaches 

 of the St. Lawrence Eiver (Chap. XXIX.). 

 Furthermore, the drowned channels among the 

 swamps of Lake St. Clair furnished additional 

 proof of the original northward discharge of 

 the Huron waters (Chap. XXVI.). 



From the structure of the terraces at 

 Foster's Flats (Chap. XIV.), and the ex- 

 cavated depth of the channel above them 

 (p. 66), I have been able to establish the loca- 

 tion of the falls when the discharge of the 

 Upper Lakes was added to the early Niagara 

 River. In soundings and borings, the nature 

 of the gorge at the Whirlpool Eapids has at 

 last been revealed (Chap. V. and XII.). My 

 soundings under the falls, the only ones that 

 have ever been made (p. 56) have brought to 

 light the reduced depth of the basin beneath 

 (p. 48). This was exceedingly important, as 

 it revealed the recent damming of the channel, 

 which raised the level of the river in the basin 

 just below the great cataract, thereby shorten- 

 ing the otherwise calculated age of Niagara 

 Falls, while they were receding the last three 

 miles, by thirty per cent. 



The ancient volume of the river has been 

 computed on a sound basis at fifteen per cent. 



of the full discharge of the four Upper Lakes, 

 an amount closely agreeing with that previ- 

 ously calculated for the Erie drainage by Mr. 

 Thomas Eussel (U. S. Lake Survey), his re- 

 sult being 16.7 per cent. (p. 252). These and 

 other features, such as the origin of the Upper 

 Rapids (p. 166 et al.), dependent upon pre- 

 glacial phenomena, cover some of the most 

 important changes in the complex history of 

 the cataract, all of which show that the energy 

 of the falls has increased tenfold, or 1,000 

 per cent. This increased power is not ques- 

 tioned, but established. 



Per contra, my critic raises three points, 

 the relative importance of which will be seen 

 upon the examination of each. One of these 

 is the relative " efficiency," or, in other words, 

 what has been the loss of work during the 

 changing energy of the cataract. He says : 

 " To say that the rate of recession is propor- 

 tional to the energy is equivalent to saying 

 that the efficiency does not change with the 

 variation of energy," but in my statement I 

 added " provided other conditions remained 

 constant" (p. 350), and my whole book is a 

 differentiation and measurement of the chang- 

 ing conditions. To the paragraph, just quoted 

 from the review, my attention was called by a 

 layman. His omission of the word " rela- 

 tive " before efficiency left on the layman's 

 mind an impression that the critic fallaci- 

 ously supiwsed that I had made a funda- 

 mental error. As the word efficiency is 

 repeated a score of times, 'the science of the 

 falls demands investigation of the point 

 raised. He urges a comparison of the rela- 

 tive efficiency of the changing energy of the 

 falls with a man-made engine, and says that 

 " the computed energy of the American Falls 

 does not differ greatly from the computed 

 energy of the main cataract during the longest 

 division of its history." Let me say that the 

 now measured discharge shows that during the 

 earlier period the volume of the main cata- 

 ract was three times that of the American 

 Falls of recent origin. 



If we are to seek analogies, let it be noted 

 that the kind of man-made engine most nearly 

 approaching a waterfall is a water-wheel or 

 turbine, though it is not so stated. Rankine, 



