IOWA ACADEMY OF SCIENCES. 00 



tiers and the charred trunk of an ancient oak, a well 

 known landmark, now stands with roots half in air. 



Two years a.o^o last September the peculiar form of an 

 island, near the inner side of this bend, attracted my atten- 

 tion. It was perhaps 2B0 feet long, crescent shaped, with 

 points turning toward the flood plain side. A heavy growth 

 of willows covered the main portion, indicating in a gen- 

 eral wa}^ the age of the island. These dwindled away 

 toward the lower end and the points of the crescent were 

 of soft newly deposited silt. A very slow drift of water 

 was noticeable on the inner side while on the outer, well 

 over toward the base of the bluff, swept the main current. 



Observing this island in the following May, it was found 

 that the horns had grown to such an extent that they were 

 both connected with the inner bank and entirely enclosed 

 a small lagoon of stagnant water. In October, 1901, one 

 year after the first observation, the lagoon had entirely 

 disappeared and a barren strip of sand marked its former 

 position. The willow covered island was now a part of the 

 flood plain. The process was probably hastened by the 

 extreme drought of the season and the consequent low 

 stage of water in the river. 



The past spring of 1902 found grass and weeds growing 

 over the greater portion of the former lagoon, and ail trace 

 of former island would soon have been lost in flood plain 

 had not the excessive rains of last July and August flooded 

 the bottom lands and removed a small amount of the 

 tilling of the old inner channel, leaving a small, stagnant 

 pool, surrounded with the tangled growth of willows and 

 weeds of the flood plain. 



Observations on other islands in the Iowa and Cedar 

 rivers, and in the Mississippi between Lansing and Musca- 

 tine, lead me to believe that this island is not a peculiar 

 form, but a type which is w^ell defined and frequent enough 

 in occurrence to deserve recognition. The history of its 

 development from sand bar and flood plain may be sketched 

 in the following three stages. 



A lodged snag or other obstacle in any well loaded 

 stream may check the current, leaving a small area of com- 



