492 A NATURALIST IN THE PACIFIC chap. 



the sea is reached, when the cloud-belt forms. On the moun- 

 tains bordering the coast of the Antofagasta province, in January, 

 the clouds gathered at an elevation of 4,000 to 5,000 feet. 

 Perhaps the best way to contrast the east and west coasts of 

 tropical South America in this respect would be to say that whilst 

 the wind blows landward in both regions, the land is the condenser 

 on the east side, and the sea, owing to the interposition of the cold 

 Humboldt current, is the condenser on the west side. 



During a fortnight spent in February at Ancon, about twenty 

 miles north of Callao, I noticed that with the prevailing cool south- 

 westerly wind the coast was clear, but it was misty at sea. On the 

 few days when there were warm westerly and north-westerly 

 breezes, the weather was thick at sea ; and if this condition was 

 pronounced, the whole coast was enveloped in mist ; but more 

 usually the coast-line was fairly clear except at the promontories, 

 along the sides of which clouds blown in from the sea rolled in 

 lines inland, not generally attaining an elevation over 300 or 400 

 feet, but sometimes reaching 900 or 1,000 feet, and gradually 

 disappearing a mile or two inside the coast-line. These sea-born 

 clouds thus vanished as they traversed the more highly heated land- 

 surface ; and the air-current continuing its inland course mounted 

 the slopes of the adjacent mountain ranges of the Andes, some 

 three or four miles from the coast, until at an altitude of some 

 5,000 or 6,000 feet condensation again occurred and the cloud- 

 belt was formed at those cooler levels. 



From the summit of a range rising to a height of about 

 2,500 feet to the north-west of Lima I had presented to me a 

 splendid spectacle, on February 12th, in the formation of the coast- 

 belt of clouds. The forenoon was clear, but about 2 p.m. the sea- 

 born clouds began to roll inland, concealing the lower two-thirds 

 of the island of San Lorenzo, which has an elevation of almost 

 1,400 feet, and completely covering up Callao and the low country 

 bordering the sea, but extending only a mile or two from the 

 coast-line. The dense cloud that covered Callao appeared, as I 

 looked down upon it from my mountain-peak, like a billowy field 

 of snow sparkling in the sun, with the summit of San Lorenzo 

 standing out like some bare alpine summit from amidst the snows. 

 Yet beneath that dazzling covering Callao lay all in gloom ; whilst 

 only six miles up the broad valley of the Rimac the city of Lima 

 stood in a blaze of sunlight, its domes and towers reflecting back 

 the light as I looked at the strange contrast it presented with the 

 buried city of the coast. The mystery of a London fog seemed to 



