Natural History. 211 



pends again on the temperature of the air and on the wind, it will 

 be found that the different degrees in which these, causes operate 

 together, will afford a satisfactory explanation of the circumstances 

 here described *. 



17. HOURLY OBSERVATIONS OP THE BAROMETER IN THE FORTRESS 

 OF CAVITE. 



These observations were made by the scientific men attached to Cap- 

 tain Kotzebue's expedition in the year 1823 1826, on the Island of 

 Luzon (14 34' north lat., arid 2399' west of Greenwich) for ascer- 

 taining the periods of its regular falling and rising during twenty- 

 four hours. The barometer was kept in a room six toises above 

 the level of the sea, in which the temperature was nearly the same 

 day and night, (about 25 Centigrade, or 77 Fahr.) and the obser- 

 vations were made on eleven different days between the 12th and 26th 

 of December. The following are the general results deduced from 

 the whole of the observations. The barometer has a maximum of 

 height at . . 9 h V 1" A. M. 



it then falls till . 4 28 6 P. M. on an average 1 . 04 line ; 



it rises again till . 9 58 3 P. M. 0.687 



and falls again till . 4 30 A. M. 



lastly it rises again till 911 A. M. on an average 0.44 5 



18. COMPARISON OP THE MEAN TEMPERATURE OF THE AIR AND 

 ! THE WATER ON THE SURFACE OF THE OCEAN WITHIN TWENTY- 

 FOUR HOURS. 



These observations were made on the expedition commanded by 

 Captain Kotzebue during the years 1823 1826. Four observa- 

 tions were made within twenty-four hours ; one half an hour before 

 sunrise, the second an hour and a half after noon, and the two 

 others at equal intervals between the afternoon's and next morn- 

 ing's observations. The result which is obtained from all the obser- 

 vations is this : in the zone from 45 N. lat, to 30 S. lat., the 

 mean temperature of the water on the surface of the ocean, whether 

 taken for the whole year, for single months, or for single days, 

 exceeds the corresponding mean temperature of the air with which 

 it is in contact. Beyond these latitudes, the means taken for twenty- 

 four hours, during the summer months, (there being no observa- 

 tions during the winter months,) varied, sometimes the one, some- 

 times the other being higher. 



The following were the highest mean temperatures for twenty- 

 four hours : 



In the northern hemisphere, of the air=27.225 C (81.0 F.) ; of 

 the water 27. 55 (81. 6 F.) 



In the southern hemisphere, of the air=26.975 C (80o53 F.) ; of 

 the water 28. 30 (82. 9 F.)t. 



* Petersburgh Transactions, 1830. f Ibid. 



P 2 



