238 Physical Observations, ^c. 



JiemarJcs. 



Latitude and Longitude. — The latitudes and longitudes given 

 in the foregoing table, were generally deduced from celestial obser- 

 vations. 



Face of the Sky. — The face of the sky was considered fair, ex- 

 cept when it was totally obscured by clouds. 



Classification of Clouds. — The classification of clouds was arran- 

 ged in the order of their ordinary elevation, after the manner of 

 Howard and Forster, viz : 



Class 1st. Cirrus, or Curl-cloud. 

 " 2d. Cirro-cumulus, or Sonder-cloud. 

 "3d. Cirro-stratus, or Wane-cloud. 

 " 4th. CuMULo-sTRATUs, or Twain-cloud. 

 " 5th. Cumulus, or StacJcen-cloud. 

 " 6th. Nimbus, or Rain-cloud. 

 " 7th. Stratus, or Fall-cloud. 



Direction of the Wind. — The direction of the wind was noted 

 after the predominant course which it blew during the day ; other- 

 wise it was regarded variable. 



Temperature of the Atmosphere. — In ascertaining the tempera- 

 ture of the atmosphere, the thermometer was constantly observed at 

 the windward side of the ship, in the shade, and there exposed two 

 minutes at each observation, in the open air, free from all possible 

 humidity and reverberation of heat arising from the body of the 

 vessel. 



Sun's Force. — ^The power of the rays of the sun also, was at- 

 tempted to be measured by means of the thermonieter ; first, by de- 

 termining the temperature of the air in the shade as above descri- 

 bed, and then by exposing the instrument a short time to the rays 

 of the sun. The increment of temperature arising therefrom, was 

 considered as the sun's force. 



Temperature of the Ocean. — As sea water is in general, a very 

 bad conductor of heat, it was deemed sufficient to expose the ther- 

 mometer about a minute at each observation in a bucket of water 

 just taken from the surface of the ocean in order to ascertain its tem- 

 perature. 



Several experiments, were made in the course of the voyage, by 

 means of a valved thermometrical sounding lead, on the tempera- 

 ture of the ocean at different depths, the most important of which, 



