January 7, 1898.} 



SCIENCE. 



29 



air, 53.5° (in lee of land); water, 57.8°. The 

 conditions of sky and wind during the day 

 were a light to fresh breeze from NE, and 

 scattering cirrus clouds or clear sky over the 

 lake. These observations, incomplete as they 

 are, are of some interest. The higher tempera- 

 ture of the water near shore, where the lake is 

 shallow, and in the Bay of Puno, which is 

 pretty well cut oflf from the main body of 

 the lake ; the slight diurnal variation of tem- 

 perature, reaching a maximum at 3 p. m., and 

 the prevailingly higher temperature of the 

 water surface over that of the air, are facts 

 that seem to be rather clearly indicated as far 

 as this one set of observations is concerned. 



On November 28th, during the return trip of 

 the steamer, observations of air and water sur- 

 face temperatures gave the following results : 

 7 a. m., air, 52.1° ; water, 56.5°. 8 a. m., air, 

 51.1°; water, 57.0°. 9 a. m., air, 51.9° ; water, 

 67.1°. 10 a. m., air, 56.7° ; water, 57.7°. 11 

 a. m., air, 52.5° ; water, 58.2°. 12 m., air, 

 55.1° ; water, 57.9. 1 p. m. (outside Bay of 

 Puno), air, 57.7°; water, 59.5°. 2 p. m. (in 

 Bay of Puno), air, 62.1° ; water, 60.4°. 5 p. m. 

 (at Puno mole), air, 49.0° ; water, 62.0°. The 

 meteorological conditions during the day were 

 an overcast sky (cirro-stratus) and light south- _ 

 east wind, or calm, till 11 a. m., when the 

 wind changed to northeast, and gradually in- 

 creased, with increasing cloudiness (alto-stratus 

 and cumulo-nimbus) unlil it reached about 

 twenty-five miles an hour. The sky remained 

 dark and threatening during the rest of the 

 afternoon, but the wind died down soon after 

 4 p. m. The water temperatures show the 

 diurnal increase up to 11 a. m., after which 

 hour, owing probably to the increasing cloudi- 

 ness and the change in wind direction, there 

 came a fall in temperature in the open lake. In 

 the Bay of Puno, as on the outward trip, the 

 temperatures were higher than in the main body 

 of the lake. Throughout the day, except at 2 

 p. m., the air temperature was below that of 

 the water. 



The clouds noted during the two trips across 

 the lake were also interesting. On the first 

 day, during the whole of which the sun was 

 shining brightly, there was a very active growth 

 of cumulus clouds over the mountains border- 



ing on the lake. These clouds were first noted 

 at 8:15 a. m. It was very noticeable, during 

 the entire day, that the cumuli were over the 

 land, where the rapid warming of the surface 

 gave rise to ascending currents of air, and 

 not over the lake, the sky over the water re- 

 maining clear, or showing light cirrus only. 

 This phenomenon is very commonly noted in 

 the neighborhood of large bodies of water, as 

 in the case of our own Great Lakes. Another 

 fact of interest was that the cumuli were bet- 

 ter developed over the eastern shore of the 

 lake, where the mountains are higher, than 

 over the western shore, which is lower. Dur- 

 ing the morning the cumuli developed rapidly 

 into cumulo-nimbus clouds, whose tops, blown 

 southwestward over the lake, soon broke ofT 

 from their bases, and dissolved as they descended 

 to lower levels, being no more supported by 

 ascending currents of air from below. About 

 2 p. m. the cumuli reached their greatest de- 

 velopment, and at 4:30 began rapidly to dis- 

 solve into long lines of degraded cumuli. The 

 height of the latter at 5 p. m., determined by 

 reference to the heights of the Bolivian Andes 

 behind them, was about 15,000 feet above sea 

 level. It was noted that there was a consid- 

 erable development of cirrus over the cumuli 

 during the morning hours of this day, thus in- 

 dicating a relation between the cumulus, formed 

 at a lower level in the ascending current, and 

 the cirrus, formed at a second higher level. At 

 this second level, as explained by Abercromby, 

 the diminished amount of vapor which the as- 

 cending current contains after the formation of 

 the cumulus reaches its second condensation 

 point, and a second layer of cloud, the cirrus, 

 is formed. 



As yet no careful study has been made of the 

 meteorology of the Lake Titicaca district, and 

 nothing definite can be said as to the influence 

 of this body of water upon the climate of the 

 surrounding country. There can, however, be 

 little doubt that the lake must modify this 

 climate to a considerable extent, although the 

 surrounding mountains would confine this influ- 

 ence to the immediate vicinity of this lake. 

 R. Dec. Waed. 



Harvard College Observatory, 

 Arequipa, Peru, December 1, 1897. 



