B.— REPOET OF THE EXPLORATIONS IN ALASKA.^ 
4. DEEP-SEA SOUNDINGS SOUTH OF THE ALEUTIAN ISLANDS. 
Approaching the Aleutian Islands, sounding was begun July 19 in latitude 52° 15' 
N., longitude 156° 37' W., 2,550 fathoms, the bottom consisting of brown ooze. This 
was the first of a series of ten soundings, extending N. 88° W. 390 miles, and made to 
further develop a remarkable submarine depression discovered by the U. S. S. Tusca- 
rora in 1874 to the southward of the Aliaska Peninsula and the easternmost of the 
Aleutian Islands. The soundings of the Tuscarora revealed a depression simply, but 
geologists have predicted the existence of a submarine trough, running parallel to the 
islands and extending probably their entire length, to the sounding of 4,037 fathoms 
made by the Tuscarora off Attu Island. The Albatross soundings, supplementing those 
of Captain Belknap, developed this predicted trough to the extent of 400 miles. Its 
direction, where determined, is S. 65° W. and N. 65° E., nearly parallel with the trend 
of the islands, the center being 60 miles from the Shumagins and 100 miles from the 
southwestern extremity of Unalashka. It is about 30 miles in width between the 
3,000-fathom lines, with a maximum depth of 3,820 fathoms in latitude 52° 20' N., 
longitude 165° W, 
Having crossed the trough and reached the normal depth west of it, the Albatross 
ran a line to the island of Unalashka, in the vicinity of Kiliuluk Bay, developing the 
contour of the slope and locating its position with reference to the land, on the’after- 
noon of July 21. At 5.30 p. m, that day a sounding was made in 28 fathoms off’ Kili- 
uluk Bay. 
* These reports have been compiled from the three separate reports of Lieut. Commander Z. L. 
Tanner, U. S. Navy, Mr. Charles H. Townsend, and Mr. A. B. Alexander, covering the different branches 
of the work prosecuted during the cruise, all of which were, however, carried on under the direction of 
Lieutenant-Commander Tanner. No material from other sources has been added. The original reports 
were in narrative form. They have been combined, rearranged, and in large part rewritten, in order 
to present the results of the explorations in more convenient form for reference. The account of the 
natural history work was furnished by Mr. Townsend; that relating to the fishing trials and the 
fisheries by Mr. Alexander, while Lieutenan*^-Commander Tanner is responsible for the hydrographic 
results, including the charts of the fishing grounds, the narrative of the cruise, sailing directions, and 
most other matters not specified above. The detailed report of the latter will be published in the 
annual report of the U. S. Commissioner of Fish and Fisheries for 1888. 
All hearings mentioned in this report are “ true” unless otherwise stated. 
Bull. U. S. F. 0., 88 2 
