110 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



J. Asmus gives, in the Annalen fUr Hydrographie, pp. 285 

 and 333, a review of various methods of graphically pre- 

 senting the deviations of ships' compasses. 



In reference to the subject of earth currents, possibly some 

 light may be thrown by the observations that have been 

 made upon them by underground telegraph lines, on the oc- 

 casion of the longitude determinations between Berlin and 

 Altona, a preliminary account of which is published by Al- 

 brecht in the Astronomische Nachrichten. The special object 

 of the investigation was to determine the nature of the curve 

 which indicated the intensity of the galvanic current on tele- 

 graph lines of different lengths, both above and below the 

 earth. It is found that the increase of intensity was decid- 

 edly less for lines below than for those above the surface. 



Professors Ayrton and Perry, of the College of Engineer- 

 ing, Tokio, Japan, communicate to the Philosojihical Magazine 

 a short note, proposing the hypothesis that the phenomena 

 of earth currents, terrestrial magnetism, and atmospheric 

 electricity are due to the fact that the earth is an electrified 

 condenser, whose capacity or potential is continually changing 

 on account of its rotation and its annual orbital motion, the 

 successive cooling and warminst of the air, the formation of 

 clouds and rain, etc., etc. These changes produce electric 

 currents tending always to restore the equilibrium, whence 

 follow the phenomena in question. They suggest that ob- 

 servations of atmospheric electricity may be used to predict 

 atmospheric changes. 



An important memoir by Edlund upon Atmospheric Elec- 

 tricity and the Aurora is published in the Transactions of the 

 Stockholm Academy, and translated in the Philosophical Mag- 

 azine. Edlund first shows that " unipolar induction " is fully 

 explained by his theory that the galvanic current consists 

 in the translatory motion of a fluid going in the positive di- 

 rection, or of two fluids following opposite directions. The 

 latest confirmation of this theory is the experiments of Lem- 

 strom. Edlund then proceeds to apply these views to the 

 earth, whose lower atmosphere is a poor conductor lying be- 

 tween two good conductors, viz., the rotating solid and liquid 

 globe and the external thin inter-planetary gas. Kegarding 

 the solid nucleus as a magnet, whose axis makes a certain 

 angle with the terrestrial axis of rotation, and whose atmos- 



