108 Discourse delivered hy Baron Humboldt to the 



isothermal lines, or lines of equal heat, shall be traced by accu- 

 rate observations, and continued at least five years, in European 

 Russia and Siberia ; when they shall have been prolonged to 

 the western coasts of America, where an excellent navigator 

 Captain Wrangel, is soon to reside, — the science of the distribu- 

 tion of heat at the surface of the globe, and in the strata acces- 

 sible to our researches, will be established upon solid founda- 

 tions. 



The government of the United States of North America, 

 keenly interested in the progress of population, and of an exten- 

 sive cultivation of useful plants, has long been sensible of the 

 advantages afforded by the great extent of its possessions from 

 the Atlantic to the Rocky Mountains, from Louisiana and Flo- 

 rida, where the sugar-cane is cultivated, to the Canadian lakes. 

 Meteorological instruments, after being compared with each 

 other, have been distributed over a great number of places, the 

 selection of which has been submitted to minute discussion, 

 and the annual results, reduced to a small number of figures, are 

 published by a central committee, which watches over the uni- 

 formity of the observations and calculations. I have already 

 pointed out in a memoir, in which I have discussed the general 

 causes upon which the differences of climate in the same lati- 

 tude depend, on how great a scale this beautiful example of the 

 United States might be followed in the Russian Empire*. 



We are happily far removed from the period when philoso- 

 phers thought they knew the climate of a place, when they 

 knew the extremes of temperature attained by the thermome- 

 ter in winter and summer. A uniform method, founded upon 

 the choice of hours, and up to the level of our recently acquir- 

 ed knowledge of the true means of the days, months, and whole 

 year, will replace the old and defective methods. By this in- 

 vestigation, various prejudices respecting the selection of objects 

 of cultivation, the possibility of planting the vine, the mulberry, 

 the chesnut, or the oak, will disappear in certain provinces of 

 the empire. To extend it to the most remote parts, we may 

 reckon upon the enlightened co-operation of many well-educated 

 young officers, with whom the Corps des Mines is honoured, 

 that of physicians animated by zeal for the physical sciences, 



• This beautiful memoir was published in toI. iv. of the New Series of this 

 Journal" 



