REPORT OF THE SECRETARY. 47 



sion, was used for the off-shore researches and in her complete equip- 

 ment of apparatus answered every demand. Tlie vessel was still in 

 command of Capt. Z. L. Tanner, an accomplished naval officer, who 

 was not only competent to take charge of the vessel in all matters of de- 

 tail, but by his thorough knowledge of mechanical appliances, and his 

 inventive i^owers, was able to devise many very important imi)rove- 

 ments in the machinery necessary for carrying on the work. 



The officers and crew of the vessel were supjdied, as before, by the 

 Navy Department, in accordance with the law of Congress. The only 

 change in the detail of officers was the replacing of Engineer Boggs 

 by Engineer Bailey. 



Fuller reference will be made in another part of this report to the 

 work of the "Fish Hawk" in connection with the hatching of food 

 tishes. The vessel was first employed in this capacity in Albemarle 

 Sound, and afterward in the Susquehanna River, two of the stations for 

 the propagation of shad. She afterward proceeded to Chesapeake Bay 

 and engaged in experiments looking towards the artificial jiropagation 

 of the Spanish mackerel. 



During the two previous seasons of occupation of the Wood's Holl 

 station by the Fish Commission a very thorough investigation was made 

 of the inshore localities, the whole of Vineyard Sound, Buzzard's Bay, 

 and other adjacent portions having been thoroughly explored in the 

 "■ Blue Light" and other smaller vessels ; it was therefore determined to 

 continue the work commenced at Newport in 1880 along the eastern edge 

 of the continental plateau representing the hundred-fathom line. This 

 plateau, as has been explained in previous reports, extends along the 

 Atlantic coast of the United States to a distance, for the most part, of 

 from 75 to tOO miles, being however considerably narrower off Cape 

 Hatteras. The depth of water increases very gradually to one hundred 

 fathoms, not much faster in most cases than one fathom to the mile, 

 affording a level almost equal to that of a western prairie. On reach- 

 ing the limit, however, the descent is very abrupt, sometimes amount- 

 ing to 1,000 fathoms, or considerably over a mile, in a few miles. Along 

 the edge of this precipice animal life occurs in vast profusion, both as to 

 the number of individuals and of species, thus furnishing a very inter- 

 esting field of research in the matter of general natural history, as well 

 as in regard to the occurrence and distribution of valuable food fishes. 



The first cruise of the " Fish Hawk" to this ground in 1881 was made 

 on the 15th July, followed by others at intervals of about once a week 

 through the summer. As the " Fish Hawk " had been built for inshore 

 work, and not with reference to standing rough weather outside, it was, 

 of course, necessary to watch carefully the ox)portunity of slipping out 

 under favorable ausi)ices, the dredge and trawl not being capable of 

 being used to advantage in a rough sea. 



Very valuable service was rendered by the Signal Office in Washing- 



