hy Alexander von Humholdt. xlix 



obtain tables of maxima and minima. In order to obtain 

 these, whenever the frigate is at anchor near any coast, but 

 particularly within the tropics, hourly observations with the 

 barometer and thermometer (the latter affixed to the baro- 

 meter, and also freely suspended in the open air), should be 

 made through several consecutive days and nights. During 

 the occurrence of an Aurora Borealis (or Australis), attention 

 should be paid to the perturbations of the magnetic variation, 

 and the magnetic intensity of the horizontal needle. Boreal 

 Auroras have been seen in the southern latitudes of the Pe- 

 ruvian Pacific, as low down as 12° 13' S. ; but the occurrence 

 of such phenomena there is of much less frequent occur- 

 rence than that of Austral Auroras in Scotland. It is 

 important to keep an exact register of the intensity of black- 

 ness in the " coalbags," when the smallest stars surrounding 

 them are still visible to the naked eye. The daily meteoro- 

 logical observations, as also those on the temperature of the 

 sea, will probably be made on board ship, in conformity with 

 the views of Lieutenant Maury, and the method agreed 

 upon at the last nautical congress. 



As I shall have long ceased to be numbered with the 

 living, when the Novara returns to Trieste, richly freighted 

 with scientific treasures of all kinds, with fresh information re- 

 lating to organic and inorganic nature, to the races of man, 

 their habits and languages, I now pray to Almighty God 

 that His blessing may rest upon this great and noble enter- 



d 



