SUMMARY OF TliE CONTENTS. 457 



On the dogs of South America ; both the aboriginal race and the de- 

 scendants of European dogs which have become wild. Sufferings 

 of cats when taken to elevations exceeding 13,000 (13,850 Eng.) 

 feet r . V > ^^'j^ . V^xi^ ;>". .:.,'.- ' v- . 98102 



The low tract of the Sahara, and its relations to the Atlas Mountains, 

 according to the latest information given by Daumas, Carette, and 

 Renou. The barometric measurements of Fournel make it appear 

 very probable that part of the North African desert is lower than 

 the level of the sea. Oasis of Biscara ; abundance of fossil salt in 

 zones or bands running from south-west to north-east. Causes of 

 the nocturnal cold in the desert according to Melloni . 102 106 



Notices of the River Wady-Dra (l-6th longer than the Rhine, and 

 dry a large portion of the year), and of the country of Sheikh 

 Beirouk, a chief independent of the Emperor of Morocco, from 

 manuscript communications of the Naval Captain Count Bouet- 

 Villaumez. The mountains north of Cape Noun (a name used by 

 Edresi, in which, since the 15th century, an allusion to the nega- 

 tive particle has been erroneously sought) attain 8600 (9166 Eng- 

 lish) feet of elevation . . . . .' r ."" . 106107 



The vegetation of the tropical American -Llanos consisting of grasses, 

 compared with the vegetation of the North Asiatic Steppes con- 

 sisting of herbaceous plants. In the last-named Steppes, and espe- 

 cially the more fertile among them, a pleasing effect is produced in 

 spring by small snow-white and red-flowering Rosacese, Amygda- 

 lese, species of Astragalus, Crown Imperials, Cypripedias, and 

 Tulips. Contrast with the desolate salt Steppes full of Chenopodi- 

 acese, species of Salsola and Atriplex. Considerations on the rela- 

 tive numbers of the prevailing families of plants. The plains 

 adjoining the Icy Sea, north of the limit determined by Admiral 

 Wf angel as that of the -growth of Coniferse and Amentacese, "are 

 the domain of cryptogamous plants. Aspect and physiognomy of 

 the Tundras, where the soil, which is perpetually frozen, is covered 

 either with a thick coating, of Sphagnum {ind other mosses, or with 

 the snow-white Cenoniyce and Stereocaulon paschale, . 107 109 



Principal causes of the very different distribution of temperature in 

 the European and American Continents. Direction and curvature 

 of the isothermal lines, or lines of equal temperature, for the entire 

 year, for the winter, and for the summer . . . . 109 119 



Are there any grounds for believing that America emerged later than 

 the Old Continent from the chaotic watery covering? . 119 121 



Thermic comparison of the- Northern and Southern Hemispheres in 

 high latitudes .. . . . . . ; * . ' > 121 123 



Apparent connection of the African sea of sand with those of Persia, 

 Herman. Belooi'histan. and the interior of Asia. On the western 

 39 



