CRUISE OF STEAMEE COEWIN EST THE AECTIC OCEAN. 121 



daily evolution being a horizontal one. The imperfect action of the compass is also a prolific 

 source of error in the ship's position. Owing to the obliquity in the direction of the magnetic 

 current as we approach the magnetic pole of the earth, and its consequent decrease of horizontal 

 attraction, the compass not only becomes sluggish in its action, but is very susceptible to local 

 errors. Large errors are produced from small ones, and small errors result from local magnetic 

 attractions which in lower latitudes would have no appreciable efi'ect, the local magnetic attrac- 

 tion remaining the same, while the horizontal attraction of the terrestrial magnetism decreases 

 as the cosine of the magnetic dip or vertical angle. The same causes interference with the accu- 

 rate location of coast lines, and no doubt accounts for errors that are attributed to other causes. 



When we consider the extent of these difficulties and the fact that they are almost constantly 

 encountered, it will readily be seen that any theory based upon a few observations taken from 

 time to time and in different parts of the Arctic Ocean rests upon slight grounds and is suscep- 

 tible of grave error, and that, unless supported by evidence of a more definite character, it should 

 be given but little weight, and in submitting the result of my observations they are subject to 

 these explanations. Perfect accuracy is not claimed. They are, however, in the main correct, 

 and, taken in connection with other facts to be presented, may be of some value. 



On the 28th of May the Corwiu anchored at Saint Lawrence Island and swung to a north- 

 erly current, which, however, slacked, and indeed entirely stopped a few hours later. This 

 change was undoubtedly due to tidal action ; although the wind was from the northward, being 

 light, it would exert but little influence on the current. 



On the 30th of the same mouth, being anchored at the West Diomede, the ice was observed 

 to be setting to the northward about 2 knots per hour, the wind blowing fresh southeast with 

 snow-squalls. 



During the night of June 3 the Corwin, while trying to get south through Bering Strait, 

 was met by a large body of ice drifting through into the Arctic Ocean from Bering Sea which 

 completely filled the strait. Being compelled to heave, until the next forenoon, the drift of the 

 vessel was noted and found to be northwest, velocity about one-half a knot per hour, weather 

 calm. 



June 7, steaming from Saint Lawrence Bay to Saiut Lawrence Island, in calm weather, a 

 current set the vessel 30 miles in an east-northeast direction in twenty hours. 



July 2, steaming from Bering Strait to Marcus Bay, time nineteen hours, the vessel was set 

 to the northeast 18 miles. There was no wind at the time, but for several days previously a 

 fresh north-northwest gale had been blowing. In passing through the strait near the Dio- 

 mede Islands at that time a stroug curreut bad been encountered, which had been the subject of 

 remark on board, some estimating it as high as 3 knots per hour. 



From 7 p. m., July 2, to 4 a. m., July 3, steaming from Marcus Bay towards Saint Michael's, 

 Norton Sound, the current set the vessel east-northeast 30 miles. 



On the afternoon of July 12 a short trip was made at Cape Prince of Wales. A strong 

 northerly current necessitated frequent working of the engine to hold the vessel in position. 

 Wind moderate and variable. 



July 30, while made fast to the shore ice at the east end of Herald Island, the current was 

 measured with the chip and line and found to be to the northward 1 knot per hour. There 

 was no appreciable change in the velocity or direction of the current during the time the Cor- 

 win remained at the island — from 9.45 p. m. until 3 a. m. The ice was setting steadily north- 

 ward during that time. 



At Cape Wankerem, latitude 08° 05', longitude 176° 30', a tidal current was observed with 

 a rise and fall at that time of about 2 feet, the flood setting along the coast to the northward. 



On the 4th of August, while cruising in the strait south of Wrangel Island, our observa- 

 tions showed a west northwest set of 12 miles, the wind light and variable. 



On the 4th and 5th of August the ship's position was determined by observation, showing 

 a current of 1 knot per hour north-northwest ; wind moderate, from east to southeast. 



On the 10th of August, while at anchor off the south coast of Wrangel Island, near the 

 edge of the ice-pack, the current was observed to be setting in a northeasterly direction, from 

 one-quarter to one-half a knot per hour. 

 S. Ex. 204 16 



