96 Y1EWS OF NATURE. 



partly with a thick mantle of Sphagnum palustre and other 

 Liverworts, and partly with a dry snowy-white carpet of 

 Cenomyce rangiferina ( Reindeer-moss), Stereocaulon paschale, 

 and other lichens. " These Tundra" says Admiral Wrangell, 

 in his perilous expedition to the Islands of New Siberia, so 

 rich in fossil wood, "accompanied me to the extremest Arctic 

 coast. Their soil is composed of earth that has been frozen 

 for thousands of years. In the dreary uniformity of the 

 landscape, and surrounded by reindeer, the eye of the travel- 

 ler rests with pleasure on the smallest patch of green turf 

 that shows itself on a moist spot." 



(18) p. 7. A diversity of causes diminishes the dryness and 

 heat of the New Continent. 



I have endeavoured to compress the various causes of the 

 humidity and lesser heat of America into one general cate- 

 gory. It will of course be understood, that I can only have 

 reference here to the general hygroscopic condition of the 

 atmosphere, and the temperature of the whole continent; 

 for in considering individual regions, as for instance, the 

 island of Margarita, or the coasts of Cumana and Coro, it 

 will be found that these exhibit an equal degree of dryness 

 and heat with any portion of Africa. 



The maximum of heat, at certain hours of a summer's day, 

 considered with reference to a long series of years, has been 

 found to be almost the same in all regions of the earth, 

 whether on the Neva, the Senegal, the Ganges, or the Orinoco, 

 namely, between 93 and 104 Fahr., and on the whole not 

 higher ; provided that the observation be made in the shade, far 

 from solid radiating bodies, and not in an atmosphere filled 

 with heated dust or granules of sand, and not with spirit-ther- 

 mometers, which absorb light. The fine grains of sand (form- 

 ing centres of radiant heat) which float in the air, were proba- 

 bly the cause of the fearful heat (122 to 133 Fahr. in the 

 shade) in the Oasis of Mourzouk to which my unhappy friend 

 Ritclre, who perished there, and Captain Lyon, were exposed for 

 weeks. The most remarkable instance of a high temperature, ID 

 an air probably free from dust, is mentioned by an observer 

 who well knew how to arrange and correct all his instruments 

 with the greatest accuracy. Rlippel found the temperature 

 110. 6 Fahr. at Ambukol, in Abyssinia, with a cloudy sky, a 

 strong south-west wind, and an approaching thunder-storm. 



