70 



No. 2. From the same place. Yery much less compact in 

 structure. The denser side represent the upper in situ ; conse- 

 quently it has always been exposed to aqueous and aerial 

 influence. 



No. 3. Foliated Travertine. From observation I am inclined 

 to infer that this structure of travertine occurs most frequently 

 where the formation closely approaches the surface, or is 

 altogether exposed. Section 4,160. 



No. 4. My observations lead me to believe that the segrega- 

 tion of these structures from the surrounding Drift material 

 progresses more rapidly when the subsoil, which is the stratum 

 in which they generally occur, is by some means for the time 

 being exposed to the atmosphere. Southern side of Section 

 4,159. 



