450 CAPE OF GOOD HOPE. 



As we were getting under way, it became evident that many of the 

 seamen had obtained supplies of grog from the shore, in spite of all 

 the precautionary measures that had been taken. One, in conse 

 quence, fell from the main-top, but, fortunately for him, while falling, 

 struck a portion of the rigging, and was thus canted into the sea, 

 from which he was picked up uninjured. When the anchor was up 

 we bore away to the northward, under all sail, with a favourable 

 breeze. 



As we passed through the tropics, many opportunities were afforded 

 us for viewing the zodiacal light, both in the morning and the even- 

 ing. Its general appearance was that of a well-defined cone, whose 

 height, as marked by the stars, remained nearly constant at 40° ele- 

 vation, and at the base 15°. Its first appearance after sunset was like 

 a broad semicircular band of light, the brightness of which increased 

 as the evening closed in, when its shape became that of a well-defined 

 cone. The light was sometimes equally diffused, and at others ap- 

 peared as if radiating through the cone. Its intensity varied from a 

 light equal to that given by a bright aurora to that of a comet, the centre 

 of the cone being often the least brilliant; and during a partially cloudy 

 evening it was sometimes so bright as to obscure stars of the second 

 magnitude. Its appearance in the morning was better defined than in 

 the evening, and the light was more of a blue than a yellow tint; the 

 altitude of the cone was greater, and its base of less extent. As we 

 changed our latitude, the position of the apex of the cone remained 

 stationary, but its inclination varied. For further information on these 

 phenomena, I must refer the reader to the volume on Physics. 



On the 9th of May, we crossed the magnetic equator in latitude 9° 

 20' S., and in longitude 16° 40' W. 



I had been led to expect in approaching the equator that we should 

 encounter strong currents setting to the north and westward, but our 

 observations showed that the current was slight and flowing to the 

 south and westward. On the 10th of May we were set forty-five 

 miles N. 85° W. ; the difference of temperature between the surface 

 water and that at one hundred fathoms depth, was fifteen degrees. 

 On the 11th we experienced no current, neither had we any on the 

 12th or 13th. On the 14th, the current set us S. 72° W., thirty- 

 two miles; and on reading the deep-sea thermometer, I thought that 

 some mistake must have been made, as it had fallen since the last 

 observation eight degrees. A second trial was therefore made ; but 

 the result was the same, making the difference between the surface 

 temperature and that at one hundred fathoms, nearly twenty-four 

 degrees. 



