10 
IOWA ACADEMY OF SCIENCE Voi,. XXVII, 1920 
The Orchidaceae of Nebraska. T. J. Fitzpatrick 
The Relation of the Smaller Forest Areas in Non-forested Regions 
to Evaporation and Movement of Soil Water. I. T. Bode 137 
Chemistry 
Simplified Electrotitration and Its Use in Determining the Iodine Ion. 
W. S. Hendrixson 
Nitrogen and Other Compounds Dissolved in Rain and Snow. Jacob 
E. Trieschmann and Nicholas Knight 159 
Soft Waters of Central New York. Nicholas Knight and J. B. Shu- 
maker 165 
An Apparatus for Determining Solubilities up tO' the Critical Tem- 
perature. P. A. Bond 
The Nitration of Hologenated Phenols. L. Charles Raiford 
The Free Energy of Dilution and the Activity of the Ions of Sodium 
Bromide. J. N. Pearce and H. B. Hart 
Geology 
Certain Post-Pliocene Deposits in Missouri. B. Shimek 
Iowa Terranes Compared with Those of Adjoining States. Charles 
Keyes 
Belated Survival of Wernerian Nomenclature. Charles Keyes 
Rectification of Iowa’s Cambric! Section. Charles Keyes 
The Use of the Terms Flint and Chert. Waldo S. Clock 167 
The Fauna of the Independence Shale. A. O. Thomas 
Nortonechinus, a Devonian Sea Urchin. A. O. Thomas 
The Corals of the Hopkinton Stage of the Iowa Silurian. A. O. 
Thomas and Beryl Taylor 
On the Occurrence of Charcoal in an Interglacial Peat Bed in Union 
County. Ralph W. Chaney 
The Content of Agricultural Geology. John E. Smith 175 
Field of Eskers in Iowa. John E. Smith 180 
A Note on a Sink Hole. E. J. Cable 181 
A Note on the Progress of Investigation of the Iowan- Wisconsin 
Border. E. J. Cable 184 
The Palisades of the Cedar. Wm. H. Norton 
A Comparison of the Nebraskan Drift with the Kansan Drift. George 
F. Kay 
The Conservation of Underground Water. James H, Fees 187 
Mathematics 
The Taxonomy of Algebraic Surfaces. R. P. Baker 197 
Physics 
Vacuum Tube Circuits as a Source of Power for Conductivity Mea- 
surements. H. A. Geauque and F. Paul Ralston 199 
The Hall Effect and the Specific Resistance of Thin Silver Films. 
G. R. Wait 203 
