596 



SCIENCE. 



[Vol. I., No. 21. 



Kilauea. The members of the expeditiou, ex- 

 cept Messrs. Preston and Brown, who remained 

 at the Hawaiian Islands to make pendnlum 

 observations, left Honolulu by the steamer 

 Zealandia on tiie 4th of June, and arrived at 

 San Francisco June 11. W. U. 



technical society a piece of apparatus, shown in 

 the illustration, which, when connected in circuit 

 with a telegraph-line, will show the varying 

 strength of the current in the line, registering 

 the results on a diagram. The earth-currents 

 are generally verj' weak, and onlj' can be 



REGISTERING APPARA TUS FOR EARTH- 

 CURRENTS.^ 



For the purpose of studying the earth- 

 currents on telegraph-lines, the instrument- 

 maker, Wauschaff of Berlin, has made for the 

 earth-current committee of the German electro- 

 umber of Zeitfichrift filr instrumenten- 



shown by the most delicate galvanometers, 

 so that no registering apparatus requiring a 

 great amount of force could be used. This 

 necessitated the use of photography. That the 

 observations might be independent of the hour 

 of the da}', an artificial source of light was 

 used. The most sensitive drj' plates were em- 

 plo\'ed, and, to keep out all extraneous light, the 



