Hot and Thermal Springs, Sfc. 255 



776 feet. But this difFerence would be smaller, if the tempe- 

 rature should suffer oscillations also at the higher point of ob- 

 servation. 



The nearer the points of observation are to the sea, the less 

 material is it at what hour of the day the observations are made ; 

 for the daily variations of temperature become smaller as we ap- 

 proach the sea-coast, and are the least considerable on the 

 open sea, especially between the tropics. Thus Humboldt ob- 

 served that the greatest daily differences of temperature, dur- 

 ing his voyage from Europe to Cumana, seldom exceeded 2°. 70 

 to 80.60.* The same has been observed by Peron,-]- Horner 

 and Langsdorf, J Lamarche, § and other travellers. |1 The 

 small islands on the ocean have no influence upon this pheno- 

 menon. 



The effect of climate is, however, felt on land, even in the tor- 

 rid zone. Thus, differences of 8°.55 to 14°.85 were observed 

 between the daily mean temperatures of Cumana and Caraccas, 

 from the 29th November 1799 to the 19th January 1800.11 

 Boussingault** found a difference of temperature of 5°.94! be- 

 tween eight o'clock in the morning and noon, on the 9th Au- 

 gust 1830, at Zupia, 3770 feet above the sea. Von Humboldttt 

 found the nights of Cumanacoa S°.60 to 5°.40, and the days 

 70.20 to 9°.0 cooler than in the port of Cumana ; and yet the 

 difference of elevation between these two places is only 1548 

 feet. On the plain of Cocollar, 2448 feet above the sea, the 

 thermometer sunk at night to 57°.20, after having been at 

 72°. 50 in the day-time ; the temperature in the night was, 

 therefore, 15°.75 lower than on the sea-coast. JJ 



In the temperate zones, where the yearly and daily varia- 

 tions of temperature are so considerable, the decrease of tem- 

 perature with the height must shew very considerable varia- 

 tions also. The corresponding observations at Geneva, and on 



" Voyage, part ii., p. 74. t Peron, Voyage, t. i., p. 32. 



X Krusenstern's Reise, vol. iii. Appendix. 



§ Aiinal. de Chim. et de Phys. voL v. 



II See Kamtz, Lehrbuch der Meteorologie, vol. ii., p. 17» 

 U Von Humboldt's Reise, part ii., p. 491. 

 •• Annal. de Ciiiin. et de Phys., vol. liii., p. 229. 

 tt Reise, part ii., p. 40. XX Ibid. p. 75. 



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