PHYSICS OF THE GLOBE. m 



phere and oceans are in motion, we have at once the phenom- 

 ena of unipolar induction ; and he then deduces the distribu- 

 tion of atmospheric electricity, terrestrial magnetism, auroral 

 display, etc., etc., in minute agreement with actual observa- 

 tions. An excellent abstract of this paper is given in the 

 Zeitschrift fur Meteorologie. 



S. Tolver Preston communicates to the Popular Science 

 Review for January a popular article on the same subject 

 i. e., the inductive effect produced by the rotation of a magnet 

 on its axis and incidentally suggests that the motion of the 

 tides may cause an electric disturbance. 



A memoir by K. S. Lemstrom on the Causes of the Earth's 

 Magnetic Condition is published as an academic disquisition 

 by the University of Helsingfors. The work is divided into 

 five chapters : first, the observed magnetic condition from the 

 earliest dates to the present time ; second, the theories of 

 Euler, Gauss, and Hansteen ; third, an attempt at explanation 

 by means of a new theory of his own; fourth, experimental 

 data tending to establish this theory; and, fifth, further con- 

 clusions from the results which he has deduced. An imper- 

 fect acquaintance with the Swedish language forbids our say- 

 ing more than that Dr. Lemstrom appears to have attempted 

 to apply Professor Edlund's views to the electric induction 

 of a rotating earth, and to have deduced a number of gen- 

 eral results agreeing closely with observed phenomena. 



The determination of the force of gravity by observations 

 of the pendulum having attained great exactness by the use 

 of the Bessel-Repsold symmetrical reversion pendulum, it has 

 become important to investigate small sources of error that 

 had previously escaped attention, and the last volume of the 

 Proceedings of the fifth General Conference of the Interna- 

 tional European Geodetic Commission contains important pa- 

 pers by C. S. Pierce, Celloria,Oppolzer, and Plantamour on the 

 corrections necessary on account of the vibrations of the sup- 

 ports upon which the pendulum rests. The general tendency 

 of these vibrations is to give the length of the seconds pen- 

 dulum too short, by a quantity that may amount to a con- 

 siderable fraction of a millimeter. 



