88 EXPEDITION TO JAPAN. 



remarkable, because, as Baron Humboldt has remarked, althougb the peak of Teneriffe is 

 seldom seen at a great distance in the warm, dry months of July and August, yet in January 

 and February, when the sky is slightly clouded, and immediately before or after a heavy rain, it 

 is seen at very extraordinary distances. This arises from the fact that when a certain quantity 

 of water is uniformly diffused through the atmosphere its transparency is thereby greatly 

 increased. 



There was a circumstance which the Commodore had observed ever since the ship left 

 Norfolk, a month before, and which surprised him not a little. He found an extraordinary 

 swell coming from the northwest, and which never intermitted for a moment until the ship was 

 fairly within the trades ; and even then its influence could be felt in the disturbance of the 

 usually regular sea produced by the periodical winds, and by the production of a disagreeable 

 cross movement of the waves. It was difficult to account for this swell so long continued ; it 

 was quite certain the ship had experienced no violence of wind sufficient to produce it in the 

 region which she had traversed, and since the 18th the winds had been quite moderate. The 

 conjecture of the Commodore was that there must have been in the higher latitudes a succession 

 of northwesterly gales, which had prevailed long enough to set in motion an ocean wave which 

 was never subdued until it came in contact with the steady, though more quiet, tropical swell. 



This swell, too, possibly had an effect in throwing further south than usual the northern 

 boundary of the trades. From the time of removing the floats up to the 20th the wind 

 continued from the southward and westward ; it then hauled to the northward and westward, 

 and finally into the northeast ; and it was not until about this period, about 8 p. m. of the 

 20th, in latitude 25° 44' north, longitude 20° 23' west, that the ship could be considered fairly 

 to have entered the trades. This is a point unusually far south for the northern boundary of 

 these winds at this season ; for it is not to be forgotten that the northern and southern boundaries 

 of the zone of the trade winds are variable. The southeast has its northern boundary furthest 

 to the north during our summer ; the northeast is then weakest. In our winter this state of 

 things is exactly reversed. In our autumn the zone of the trades reaches its greatest northern 

 declination ; and in our spring it is at its utmost southern limit. 



On the 22d of December, the Commodore issued a general order, promulgating the directions 

 of the Secretary of the Navy forbidding communications to the jjublic prints at home touching 

 the movements of the squadron, and prohibiting also such infomation through the medium of 

 private letters to friends. The Secretary also required that private notes and journals kept by 

 any members of the expedition should be considered as belonging to the government until their 

 publication should be expressly permitted by the Navy Department. 



A second general order, issued the next day, was as follows : 



" Entertaining the opinion that the talents and acquirements of the officers of the squadron, 

 if properlj directed and brought into action, will be found equal to a plain and practical 

 examination and elucidation of the various objects pertaining to the arts and sciences that may 

 come under their observation during the present cruise, and being aware of the limited 

 accommodations of the vessels under my command, I have invariably objected to the employ- 

 ment of persons drawn from civil life to conduct those departments more immediately connected 

 with science. 



"Therefore I have to request and direct, that each officer of the respective ships will employ 

 such portions of his time as can be spared from his regular duties and proper hours of relaxation, 

 in contributing to the general mass of information which it is desirable to collect ; and in order 



