202 McGee and Call—Zoss of Des Moines, Iowa, 



ations of Max Schuster,* the second is explained by the multiple 

 twinning of the crystals. 



When placed in a delicately graduated Thoulet's fluid, so 

 prepared that orthoclase will rest near the surface an. 1 labra- 

 donte near the bottom, the crystals found the exact level of 

 fragments of transparent albite from Haddam, sp. gr. 2-62, and 

 remained attached to them as if they were so delicately freed 

 from outward uttra.-tion rha! they gravitated toward each other, 

 borne of the crystals having diabantite adherent to them sank 

 to the level of quartz, sp. gr. 2-64, but all were separated by a 

 broad interval from the other triclinic feldspars. The position 

 of these crystals is interesting from a paragenetic point of 

 view. The cavities are tapestried on all sides by the v. 

 and the albites rest, often very loosely, upon it, and while 

 forming projected freely into the interior as is shown by their 

 vuess and perfection of form and polish. The last of 

 the diabantite seems sometimes to fill the cavities into which 

 the albites project, but this could not be made certain. As the 

 albite probably demands elevated temperature and increased 

 pressure for its formation, the diabantite upon which it rests 

 signed to the time following immediately upon the 

 - -mile its heat still intensified the 



3 continued.) 



A ? T " FK'^" the LUss and ass oa'ated Deposits of Des Moines; 

 Vn & McGe t E ' of Farle * Iowa > and E - Ellsworth Call, 



[Read before the Iowa Academy of Sciences, May 31, 1882.] 



been noted by F. M. Witter,f the junior author of tin 

 and a number of local geologists. Late in 1881 the junior 

 author observed that m certain sections that deposit appeared 

 to be overlain by a bowlder-bearing stratum; and the present 

 communication embraces the results of a series of investigations 

 suggested by this observation. 



g geographical features the aceompanvin- map i 



-* *Mk county in Andreas's Atlas ;{ 



been added from observation 



a copy of a part of the map of Polk county in And 

 though a few minor details ' 



*Tsch. Min. Mitth.. 



merican Naturalist. > 

 . T. Andreas' Illustra 



