54 8 The Smithsonian Institution 



ports on the progress of vulcanology and seismology, prepared 

 by Professor C. G. Rockwood, Jr., of Princeton University. 

 Modern seismology is now represented in the collections of 

 the Smithsonian Institution by a very complete suite of seis- 

 mological apparatus, devised by Milne, Gray, Ewing, and 

 others, and mostly used in the investigation of seismic phe- 

 nomena in Japan. 



Other phases of terrestrial physics are represented in a 

 paper published in 1860 in the "Contributions," on the 

 " Fluctuations in the Level of North American Lakes," by 

 Whittlesey, and one on " Tidal Observations in the Arctic 

 Seas," published at the same time, in the same place. To 

 these should be added a very valuable paper, which appeared 

 in the Report for 1874, on "Tides and Tidal Action in Har- 

 bors," by J. E. Hilgard. Closely related to these are the 

 monographs by General J. G. Barnard, of the United States 

 Engineers, the earliest being on the " Problems of Rotary 

 Motion presented by the Gyroscope, the Precession of the 

 Equinoxes and the Pendulum," which was published in the 

 "Contributions" in 1871. It consists, properly, of three 

 papers, which were separately read before the National 

 Academy of Sciences. The object of the first was to deduce 

 the analytical expression of the precession of the equinoxes 

 directly from the theory of the gyroscope, a suggestion of 

 which the author had made as early as 1857 in an article in 

 the American Journal of Science. The second part was a 

 mathematical examination and analysis of the " Motions of 

 Freely Suspended and Gyroscopic Pendulums," and " On the 

 Pendulum and Gyroscope as Exhibiting the Rotation of the 

 Earth," and is an elaborate discussion of the very interesting 

 methods of proving the earth's rotation first suggested by 

 Foucault. The third part is "On the Internal Structure of 

 the Earth as Affecting the Phenomena of Precession and 



