A Mystery of Crowds 20 



late the flow of population through the more 

 crowded thoroughfares. (We need not for pres- 

 ent purposes concern ourselves about the com- 

 plex middle -currents of the living river, with 

 their thunder of hoofs and wheels : I shall speak 

 of the side-currents only.) On either footpath 

 the crowd naturally divides itself into an upward 

 and a downward stream. All persons going in 

 one direction take the right-hand side ; all going 

 in the other direction take the left-hand side. 

 By moving with either one of these two streams 

 you can proceed even quickly; but you cannot 

 walk against it : only a drunken or insane per- 

 son is likely to attempt such a thing. Between 

 the two currents there is going on, by reason 

 of the pressure, a continual self-displacement 

 of individuals to left and right, alternately, 

 such a yielding and swerving as might be repre- 

 sented, in a drawing of the double-current, by 

 zigzag medial lines ascending and descending. 

 This constant yielding alone makes progress 

 possible: without it the contrary streams would 

 quickly bring each other to a standstill by lateral 

 pressure. But it is especially where two crowd- 

 streams intersect each other, as at street-angles, 

 that this systematic self-displacement is worthy 



