January 21, 1898.] 



SCIENCE. 



97 



drifting white sand, which gives the whole re- 

 gion a most inhospitable appearance. The in- 

 struments at Mejia are the dry- and wet-bulb 

 and maximum and minimum thermometers, 

 rain-gauge, wind-vane, Pickering sunshine-re- 

 corder, barograph, thermograph and hygro- 

 graph. Observations are made thrice daily, at 

 8 a. m., 2 and 8 p. m., and include, besides the 

 records of the instrumental reading, observa- 

 tions of clouds (kind, position, amount) and of 

 wind velocity (estimated). This seacoast sta 

 tion is especially valuable as giving data con- 

 cerning the climatic conditions of the desert belt, 

 where its climate is modified by the proximity 

 of the ocean. 



The next station inland from Mejia is at La 

 Joya, a railroad station distant from the ocean 

 about 40 miles, and situated in the center of 

 the elevated pampa of Islay, at an altitude of 

 4,141 feet above sea-level. This pampa lies 

 east of the coast range of mountains, and is 

 almost completely devoid of vegetation. It is 

 surrounded by hills, and is very largely covered, 

 towards its eastern margin, with the curious 

 traveling sand crescents known as medanos, 

 which move across the desert from south 

 to north, in the direction of the prevailing 

 day wind. These medanos are composed of 

 white sand, apparently quite different from that 

 which makes up the rest of the desert surface, 

 and they are a very striking feature of the land- 

 scape. The meteorological conditions at La Joya 

 are very interesting, and the records will furnish 

 abundant data for the study of what we may 

 call desert meteorology, which would include such 

 characteristically desert phenomena as mirages 

 and dust whirls. The instruments at La Joya 

 are similar to those at Mejia. 



The central station is at the Observatory, in 

 Arequipa. Arequipa is situated at a distance 

 of about 80 miles, in a direct line from the 

 Pacific Ocean, and lies on both sides of the 

 river Chile, the water from which is extensively 

 used in irrigating the neighboring fields. Al- 

 though the surrounding pampas can support 

 only scant vegetation, the city itself lies in the 

 midst of green fields of wheat, barley, Indian 

 corn and alfalfa. The Observatory is built on 

 high land overlooking the city, and stands at 

 an elevation of 8,050 feet above sea-level, being 



about 500 feet above the city. Its exact location- 

 is lat. 16° 22' 28'' S.; long. 4 h., 46 m., 12 sec. 

 To the north, about 12 miles distant, rises Char- 

 chani, 20,000 feet high; to the northeast, 10 

 miles away, is the Misti, 19,200 feet; and to 

 the east comes the serrated ridge of Pichu-Pichu^ 

 an extinct volcano, 18,600 feet high. Arequipa, 

 at a considerable distance from the ocean, and 

 in close proximity to several high mountains, 

 presents meteorological conditions, a study of 

 which is peculiarly interesting. Observations 

 are made at 8 a. m., 2 and 8 p. m. daily. The 

 instruments in use are the following : Wet- and 

 dry-bulb, maximum and minimum, solar- and 

 terrestrial-radiation thermometers ; mercurial 

 barometers, rain-gauge, anemometer and ane- 

 moscope, Pickering sunshine recorder, baro- 

 graph, thermograph and hygrograph. The 

 observations include, in addition to readings of 

 the instruments, tri -daily records of clouds- 

 (kind, position and amount), and of the visi- 

 bility of the three neighboring mountains. 

 Earthquake records include two observations 

 daily of the seismograph and seismoscope, and 

 two daily records are also made of changes ia. 

 the level of the ground. 



The fourth station, still farther inland, is on 

 the so-called Pampa de los Huesos, about 30 miles 

 northeast of Arequipa, at an elevation of 13,400 

 feet above sea-level. This^pampa is composed 

 of volcanic sand and ashes, and is almost com- 

 pletely barren. Thei-e being no possibility of 

 securing an observer in this desolate region, 

 readings of the wet- and dry -bulb thermometers 

 are made whenever a visit to the shelter is pos- 

 sible, at which times, also, the sheets of the 

 barograph and thermograph are changed. 



On the flank of the Misti above the Pampa de 

 los Huesos, at a height of 15,700 feet, is the 

 fifth station, known as ' Mont Blanc,' because 

 the altitudes of this station and of that on the 

 summit of Mont Blanc are almost exactly the 

 same. The ' M. B. ' shelter, as it is called for 

 brevity, is at a distance of about 300 feet from the 

 hut where observers from Arequipa, on their 

 way to visit the meteorological station on the 

 summit of the Misti, spend one night. The 

 instruments are wet- and dry -bulb and maximum 

 and minimum thermometers, thermograph and 

 barograph ; and this station is visited, as is that 



