TABLE OF CONTENTS. 1 



ARTICLE I INTRODUCTION. Pp.16. 

 Advertisement 

 List of Officers of the Smithsonian Institution 



AllTICLE II. 



ARTICLE III. 



(No. 240.) PROBLEMS OP ROTARY MOTION PRESENTED BT TIIE GYROSCOPE, 

 THE PRECESSION OP THE EQUINOXES, AND THE PENDULUM. By Brevet 

 Maj. -General J. G. BARNARD, Colonel of Engineers, U. 8. A., A.M., 

 LL.D., Member of National Academy of Sciences. 1871-1873. 4to. 

 pp. 71 



The Precession of the Equinoxes and Natation as resulting from the Theory 

 of the Gyroscope ....... 



On the Motions of Freely Suspended and Gyroscopic Pendulums, and on 

 the Pendulum and Gyroscope as exhibiting the Rotation of the Earth . 



On the Internal Structure of the Earth considered as affecting the Phe- 

 nomena of Precession and Nutation ..... 



New Addendum ........ 



(No. 241.) A CONTRIBUTION TO THE HISTORY OP THE FRESH- WATER A i..,.i: 

 OP NORTH AMERICA. By HORATIO C. WOOD, Jr., M.D., Professor of 

 Botany, and Clinical Lecturer on Diseases of the Nervous System in 

 the University of Pennsylvania ; Physician to the Philadelphia Hospital, 

 etc. October, 1872. 4to. pp. 274. Twenty-one colored plates. 

 Preface ......... 



Introduction . . ..... 



Fresh-Water Algae of the United States . 

 Class Phycochromophyceae 

 Order Cystiphorse 



Family Chroococcaeeae 

 Order Nematogenem 



Family Oscillariacete ...... 



Family Nostochacete . . . . 



Family Rivulariaceffi 



Family Scytonemaceae ... 



Family Sirosiphonacctc ... 



Class Chlorophyllaceaj . . . 



Order Coccophycesc ... 



Family Palmellacee ..... 



Family Protococlaceae 



Family Volvocineae ...... 



Order Zygopbyceae ... 



Family Desmidiaceic ...... 



Family Zygnemaceae ...... 



PAOI 



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100 



159 



Each memoir li separately paged and indexed. 



