40 THE PATH OF SCIENCE 



In spite of the repetition of the rise and fall of art, of lit- 

 erature, and even of civilization as a whole, mankind has 

 made progress through recorded history. Cities and empires 

 have risen, and cities and empires have fallen. Artists, en- 

 gineers, and philosophers have lived and worked, died and 

 been forgotten, but none the less, some systematic secular 

 change has occurred. If the circle has come its full round, 

 the pattern of history is a spiral, not a ring, for the start of a 

 new cycle of civilization is never identical with that of the 

 last; and, on the average, each cycle starts from a point a 

 little above that of the preceding cycle, so that the successive 

 turns of the spiral are not coplanar, and the pattern may be 

 more accurately depicted as a helix.* All through the paleo- 

 lithic period, little change occurred. Nevertheless, there 

 came a time when the production of the flint tools improved, 

 and we recognize that this phase lies above that of the pre- 

 ceding phase, a change recognized by the term "neolithic" 

 instead of "paleolithic." Then somewhat more rapid prog- 

 ress is made; and in one or two more turns of the helix we 

 reach the point where agi'iculture is discovered, where the 

 villages and towns come into being, and then where writing 

 is invented. And now successive turns rise more rapidly from 

 each other, and we see that it is necessary to consider the 

 meaning of this vertical component of our diagram. 



Since time is represented by the angular co-ordinate, the 

 vertical component must be the level of achievement, dif- 

 ferent according to the field of accomplishment selected- 

 sculpture, architecture, engineering skill, literature, and so 

 forth. This is the level of civilization as a whole and not 

 that of any single component. In many fields, there is little 

 or no secular improvement— in the art of sculpture, for in- 

 stance—and there must, therefore, be some factor in the ver- 

 tical component of the helix that has steadily increased and 



* The frontispiece is an attempt to realize this graphically. It is a 

 photograph of a helix of wire. The lower coils are close together, and, 

 as they rise, they are distorted and even overlap, but finally the vertical 

 component increases rapidly. 



