128 MY LIFE [Chap. 



to be seen nearly from top to bottom — a most impressive 

 sight. 



When I got back to Washington it was snowing hard, and 

 the whole country was more wintry-looking than at Niagara, 

 four degrees further north. I at once went to the Geological 

 Survey Library to look up recent works on Niagara, and 

 had an interesting talk with Mr. McGee about it. He told 

 me that the centre of the Horse-shoe Fall has receded about 

 two hundred feet in forty years. The Potomac falls, which 

 are in gneiss rock, have receded quite as fast. The conditions 

 that combine to produce the recession of waterfalls are 

 numerous, and so liable to change, that it is impossible to 

 trust to conclusions drawn from observations during limited 

 periods. It is evident, for example, that while the Canadian 

 falls have receded nearly one-third of a mile, the American 

 falls have not receded more than ten or twenty feet. 



Although I did not have a single lecture engagement at 

 Washington, I read two short scientific papers there. There 

 was a Woman's Anthropological Society, which invited me 

 to address them, and being rather puzzled what to talk about, 

 I made a few remarks on " The Great Problems of Anthro- 

 pology." These I defined as the problem of race and the 

 problem of language. On the first point I stated that there 

 are three great races or divisions of mankind clearly definable 

 — the black, the brown, and the white, or the Negro, Mon- 

 golian, and Caucasian. If we once begin to subdivide beyond 

 these primary divisions, there is no possibility of agreement, 

 and we pass insensibly from the five races of Pritchard to the 

 fifty or sixty of some modern ethnologists. The other great 

 problem, that of language and its origin, was important, 

 because it was, above all others, the human characteristic, 

 and was the greatest factor in man's intellectual develop- 

 ment. I then laid down the outlines of the theory of mouth- 

 gestures, which I afterwards developed in my article on " The 

 Expressiveness of Speech," showing how greatly it extends the 

 range of mere initiative sounds (which had been ridiculed by 

 some great philologists) and affords a broad and secure 

 foundation for the development of every form of human speech. 



