ATLANTIC SPRING TEMPERATURE. 5' 



for the assumed uniform pressure that higher or lower 

 amount which is known to prevail at given seasons. 

 Such a correction could not, of course, be made avail- 

 able in very variable climates, such as that of the 

 British Islands, but might be applied in many parts 

 of the broad zone lying within 40° of the equator. 



Soon after ten p.m. on the 21st we were abreast of 

 the bright light which marks the harbour of St. 

 Michael's, but, the night being dark, we saw very little 

 of that or ^ny other of the Azores group. The spring 

 temperature of these islands is about the same as that of 

 places in the same latitude in Portugal ; but it appears 

 that the cooling effect of the east and north-east 

 winds prevailing at that season must in the mid- 

 Atlantic extend even much farther south. With 

 generally fair settled weather, the thermometer rose 

 very slowly as we advanced towards the tropics. 

 Between the 1 8th and 24th of March, in passing from 

 50° to 29" north latitude, the mean daily temperature 

 rose only from about 55° to about 65° Fahr. — the 

 thermometer never rising to 70°, nor falling below 

 52°. Notwithstanding the relatively low temperature, 

 a few flying-fish were seen on the 24th — rare, it is 

 said, outside the tropics so early in the year, though 

 sometimes seen in summer as far north as the Azores. 

 On March 25th we, for the first time, became con- 

 scious of a decided though moderate change of 

 climate. The thermometer at noon stood at 71°, and 

 was not seen to fall below 10° until, some three weeks 

 later, off the Peruvian coast, we met the cold antarctic 

 current which plays so great a part in the meteorology 

 of that region. We were now in the regular track of 



