CONTENTS. 4 



LuEDEKiNG, C. — The Hydration of Colloids 375 



NiPHER, Francis E. — Report on (Missouri Rainfall, with 



Averages for Ten Years ending December, 1887 3S3 



NiPHER, Francis E. — On the Output of the Non-condens- 

 ing Steam Engine, as a Function of Speed and Pres- 

 sure 434 



LuEDEKiNG, C. — The long-continued Action of the Electric 



Discharge on iodine 445 



Robertson, Charles — Flowers and Insects : Umbel- 



liferc^ 449 



Nipiier, Francis E. — Winter Temperatures 461 



Engelmann, Dr. G.J. — Frederick Adolphus Wislizenus. . 464 

 Nipher, Francis E. — Surface Integrals in Meteorology ... 469 

 Luedeking, C. — On the Analysis of the Barium Group.. . 471 

 Hitchcock, A. S. — Contrib. from Shaw School of Botany, 

 No. 7) — A Catalogue of the Anthophyta and Ptcrido- 



phyta of Ames, Iowa 477 



DuFFEY, J. C. — Transformations of a Carabid (Flochionus 

 timidus), and Observations on a Coccinellid enemy of 



the Red Spider 533 



Pammel, L. H. — (Contrib. from Shaw School of Botany, 



No. 8) — On the Seed-coats of the Genus Euphorbia. . 543 

 Robertson, Charles — Flowers and Insects, Asclefiada- 



cece to Scrophulariacece 569 



Pritchett, H. S. — A Formula for Predicting the Popula- 

 tion of the United States 599 



Pritchett, H. S. — Observations of the Transit of Mercury, 



May 9, 1 89 1 609 



VoGDES, A. W. — Notes on some new Sedalia Trilobitcs . . 615 

 Nipher, Francis E. — On Certain Properties of a Field of 



Force due to a Single Mass 619 



Journal of Proceedings xxxi-lvi 



Exchanges received, i888-'9i ■. . . . 17-33 



Donations, " " 34~37 



Contents. 3 



General Index 5 



