OLD FAITHFUL 121 



at that depth, is increased enormously, until at 

 last the steam simply explodes, as it would in a 

 boiler, forcing out before it the contents of the 

 tube until such time as the pressure is relieved, 

 and the process renews itself. The greater the 

 heat below, and the smaller the tube, the greater 

 the force with which it is expelled. Thus the 

 Giant Geyser rises to a height of two hundred and 

 fifty feet; the Giantess to two hundred, while Old 

 Faithful varies from one hundred and sixty to one 

 hundred and seventy-five feet. 



Once a Chinese washerman in the Park had a 

 brilliant thought. He would build his laundry 

 over one of those warm springs. Fuel would cost 

 nothing. So thought — so done. The first wash- 

 ing, well soaped, went in. In about five minutes 

 the spring became a geyser, blew the building, 

 washing and Chinaman a hundred yards, and then 

 cheerfully resumed its ordinary boiling and 

 bubbling. The explanation was that the soap 

 created a viscous surface on the water, prevented 

 the escape of steam from below and turned the 

 spring into a geyser. Any interruption of the 



