154 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



altogether against the unprotected iron, which is electro-positive to 

 magnetic oxide. 



It appears, however, that the neighborhood of copper or its compounds 

 in sea- water would probably be destructive to a surface of magnetic 

 oxide, as was the case in the experiment noted. Whatever galvanic 

 action occurs in such a couple must necessarily be at the expense of the 

 magnetic oxide. The presence of zinc, tin, or lead would probably be 

 protective to the iron. . 



In conclusion I may say that this examination indicates that the 

 magnetic oxide is an effective protection against the ordinary processes 

 of iron rust; that the kind of galvanic action which occurs between iron 

 and its magnetic oxide in presence of sea- water is altogether at the 

 expense of the former ; that the neighborhood of copper, nickel, silver, 

 or ether metal electro-negative to the magnetic oxide of irou in presence 

 of sea- water will lead to the speedy destruction of the magnetic oxide; 

 and, finally, that the specimens thus far examined appear to have been 

 exposed to the protective process for too short a time to insure full 

 security under the conditions presented by the requirements of the Fish 

 Commission. 



Smithsonian Institution, 



Washington, D. C, February 23, 1885. 



33.— REPORT OF OPERATIONS AT TDE HATCHING ESTABLISHMENT 

 FOR MARINE FISHES, ARENDAL,, J 884.* 



By G. M. DANKEVIG. 



To tlis Management of the Arendal and Omegn branch of the Society for the 

 Promotion of the Noncegian fisheries : 



I have the honor to submit to the board of managers the following 

 report of the operations of the hatching establishment during the year 

 1884 : 



Cod. — On account of the easily foreseen difficulties in procuring the 

 necessary number of parent fish, the purchase of these was commenced 

 at the beginning of the year and continued without interruption until 

 about the middle of the month of April. The fish obtained were, how- 

 ever, very small, and yielded in consequence little spawn, which will, 

 to some extent, explain the comparatively small result which the estab- 

 lishment has to show for the present year. It will be evident also, from 

 the detailed report given below, that there were other causes which 

 operated strongly in the same direction. Besides, we should not leave 

 out of consideration the fact that, as director of the establishment, I 

 had to confront an entirely new experiment, and that, in addition to 

 theoretical knowledge, there is required also a practical acquaintance 



*Beretning over Virksomheden ved TJdklcekmngaanstalten for Saltrandsfisk. Arendal, 

 1884. Translated from the Norwegian by Tarleton H. Bean. 



