The Underground Drainage 



our only hope of penetrating beyond this chamber lay in 

 following the canal, and this we proceeded to do im- 

 mediately after finishing our lunch. 



Having once more launched the canoe, we passed 

 along the shore and followed the canal to the mouth of 

 the tunnel. This we found to be narrow but lofty, and, 

 unlike those of the one by which we entered, the sides 

 sloped together near the top, eventually meeting about 

 20 feet above the water. 



Several times the tunnel turned suddenly at right 

 angles and widened somewhat, but at about a quarter of 

 a mile from the mouth we came upon a barrier of tufa 

 which stretched completely across the stream, and over 

 which the water poured in a thin sheet. The barrier 

 was 10 feet in height, and it was with considerable 

 difficulty that two of us effected a landing upon it, and 

 were able to traverse it from end to end. Above this 

 weir-like barrier the canal continued as far as our lights 

 were able to penetrate, and as the water was deep on 

 the upper side and again filled the tunnel from side to 

 side, we went back to consult with the others as to what 

 should next be done. We did not care to take the risk 

 of swamping or damaging our canoe by trying to haul it 

 over the barrier, and so decided to abandon the explora- 

 tion for the day, but to return on the morrow to see if 

 some other passage could not be found. 



The wall or barrier of tufa was such as we knew to 

 be formed in similar situations in the following manner. 

 The stream originally flowing over its rocky bed reached 

 a low waterfall probably not more than a foot or so in 

 height. As the water poured over the lip of the fall the 

 disturbance caused the escape of some of the carbonic 

 L 161 



