92 Transactions Tennessee Academy of Science. 



Some Neglected Principles of Ph37siograpn5) 



By A. H. Purdue, State Geological Survey. 



(Abstract.) 



In this paper there are briefly considered some characteristics 

 of entrenched meanders, the origin of limestone sinkholes, and 

 (in the opinion of the speaker) some anticline valleys, and pos- 

 sibly of some transverse drainage. 



Entrenched meanders, instead of commonly having the V- 

 shaped form often attributed to them in the class-room, usually 

 have unlike slopes on opposite sides of the stream in any given 

 cross section, those on the outside of the curve being steep, and 

 those on the inside more or less gradual. The reasons for this 

 were given by the speaker. 



Limestone sinkholes are seldom formed by the collapse of 

 cavern roofs, as is generally supposed. Instead, most of them 

 owe their existence to solution at the surface, by descending 

 waters that are focused about openings, formed by jointing. 



The common explanation of anticlinal valleys is that streams 

 1/ave gradually shifted from synclines to anticlines, the shift- 

 ing having been invited by the excessive fracturing of the latter 

 over the former. The writer believes that most anticlinal valleys 

 have had a different history. It will be conceded that most folds 

 liad their inception while yet submerged. This granted, the first 

 part of the folds to appear at sea level were the crests of the anti- 

 clines. E.xcept at considerable depths, all the sedimentary mate- 

 lial but lliat of calcareous nature was in the incoherent state at 

 tlie time of elevation, and consequently was easily eroded. As 

 soon as the anticlinal crests came within the effective force of the 

 waves, they were ilu'reby Iruiicaled. 'i'he rate of rise was greater 

 than we are accustomed to admit, if the truncation did not for a 

 long time ef(ual the elevation. As the truncated material was 

 shiftrd Id lln' syiu-linal Irdiighs. llie whole process was a leveliig 



