FROM CORUNNA TO PUERTO CABELLO. 267 



interest to the scientific investigator plants, mountains, rocks, 

 and above all a new order of human kind, the friendly Indians 

 and the tribes of the Caribs. 



' I have now been for a couple of months in this new quarter 

 of the globe the Terra Firma of South America, and together 

 with my travelling companion, Bonpland, who has proved him- 

 self an indefatigable worker, I am in the enjoyment of the best 

 possible health. We have already collected a great number of 

 plants, insects, and shell-fish : I have made several drawings, and 

 been much occupied with experiments for ascertaining the 

 composition of the atmosphere. 



' Just now I am trying to investigate the problem why the 

 refraction of light should be less in this zone of high 

 temperature than with us. This effect cannot be ascribed 

 solely to the heat. Much, no doubt, is due to hygrometric 

 conditions, for I am of opinion that the greater damp of this 

 region of the globe diminishes refraction. 



6 During the voyage I was much occupied in registering the 

 temperature of the ocean and in ascertaining its specific 

 gravity by means of one of Dollond's excellent balances. The 

 idea suggested by Franklin and Jonathan Williams of taking 

 soundings with a thermometer attached to the lead is as 

 ingenious as it is happy in conception, and will eventually 

 become of great importance to navigation. I undertook 

 several experiments on board ship with Hadley's mirror 

 sextant. I haVe an eight-inch one by Eamsden with a silvered 

 arc divided to 20 seconds. I have besides a two-inch sextant 

 by Troughton, which I call my snuff-box sextant : it is really 

 incredible what may be accomplished with this little instrument. 

 A single set of observations taken by it of the altitude of the 

 sun when passing the prime vertical will give the correct time 

 within two or three seconds. If this accuracy be purely 

 accidental, it must at least be admitted that the chance happens 

 very frequently. 



' I systematically kept an astronomical journal, and when- 

 ever the weather and the calmness of the ocean permitted I 

 made observations of the latitude and longitude of the ship or 

 of the places where we landed ; I also observed the inclination 



