478 CAPE OF GOOD HOPE. 



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 

 evenino- 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. 



The northeast trades were entered on the 15th of May ; the diffe- 

 rence of temperature being similar, and the current setting us to the 

 southwest and west thirty-four miles. On the 16th we crossed the 

 equator, in longitude 30° 30' W. At 6 a. m., the same day, the ther- 

 mometer at one hundred fathoms depth rose to 68-5°, being the same 

 temperature as that experienced before the 14th, when we encountered 

 the cold submarine current. We had crossed this current in a direc- 

 tion nearly at right angles to its flow, and I estimated its width at two 

 hundred miles. The current on the 19th still set to the southward; 

 the difference between the deep-sea and the surface temperature being 

 found to be again twenty-four degrees. This w-as also the case on the 

 20th, on which day I tried the temperature at fifty fathoms depth, and 



