22 On the Heat of Springs, [Jult, 



The greater trie difference of resistance in different media, at a 

 less angle will the light be reflected : thus out of water into air, 

 where the refraction is nearly as three to four, it will be reflected 

 at an angle of 48° 35° ; out of glass into air, where the refraction is 

 to incidence as 20 to 31, light will be reflected at an angle of 

 40° 20°. 



Article IV. 



Observations on the Heat of Springs, and on Vegetation, in order 

 to determine the Temperature of the Earth and the Climate of 

 Sweden. By George Wahlenberg, M.D. Fellow of the Koyal 

 Academy of Sciences of Stockholm.* 



Dr. Wahlenberg, who spent the last winter in Berlin, and is 

 at present travelling through Switzerland, prepared the following 

 treatise for the Annalen der Physik. It is scattered through the 

 memoirs of the Academy of Sciences of Stockholm for the last 

 three years, and deserves to be exhibited in one connected view. 

 Dr. Wahlenberg has treated of the temperature of the earth in the 

 north of Sweden with care and skill ; not as a mere object of 

 curiosity, but as a physical phenomenon, which constitutes a part 

 of the physical constitution of the earth. I think I may flatter 

 myself that my travels in the north have induced him to undertake 

 these investigations. Mr. Von Humboldt's views, in his Geography 

 of Plants, respecting the southern line of plants, have been followed 

 out here with so much knowledge and exactness, that the results, I 

 think, ought to find a place in the Annalen der Physik. Plants are 

 now the objects by means of which accurate meteorological conclu- 

 sions are to be drawn ; and philosophers may in a few weeks acquire 

 as much knowledge of plants as is necessary for these kinds of in- 

 vestigation: and in how different a light does meteorology, degraded 

 as it is by philosophical quackery, appear, when we draw our con- 

 clusions from so easy, but yet so accurate, a medium. Of how 

 much more importance would it be for the philosophers of Leipzic 

 to investigate their climate by the distribution of plants ; as, for 

 example, to ascertain whether the chrysocoma lynostis and the 

 onosma echioides would spread in it, than to employ themselves in 

 determining whether the conjunction of Jupiter and Venus would 

 throw ihe interior organic parts into mighty labour in order to bring 

 forth a mouse? Wahlenberg's experiments, how from springs, 

 which are so very variable in their temperature, the mean tempera- 



» Translated from Gilbert's Annalen tier Physik for 1812, vol. xli. p. 113. Th« 

 introduction is by Von Buch. The pap'-r itself consists of a collection of disser- 

 tatinna published by Wahlenberg at different times in the Memoirs of the Swedish 

 Academy. An abstract of some of them by Mr. Driandcr was inserted at the end 

 of Linnzeus' Travels in Lapland. 

 1 



