THE GEOLOGIST. 



35 



author that the phenomena to which we have just aUuded remmd 

 us of the instability of the present order of things, and the changes 

 to which the outlines and configurations of continents ai'e probably 

 still subject at long intervals of time. 



Our distinguished friend. Dr. Van den Coi-put, duiing a recent 

 travel in Africa, has paid particular attention to the sand of the 

 great Desert of Sahara. The samples he has examined were col- 

 lected from the north-easterly regions of the great desert, which 

 covers a tract of land of about 300,000 square leagues, a 

 superficies nearly three times that of the Mediterranean.* This 

 sand is so white and of so fine a graiu, that one could easily 

 mistake it for pulverized glass. — Ehrenberg once professed the 

 opinion that the sand of Sahara was chiefly fonned of the remains 

 of hosts of microscopic animalculi, resembling those discovered in 

 the calcareous formations on both shores of the Nile. — Van den 

 Corput assures us that this opinion, to say the least, is extremely 

 exaggerated. In the microscopical investigations to which he 

 submitted the sand of Sahara he discovered neither Infusoria, 

 Foraminifera, or Diatomacese, and very few, if any, organic or calca- 

 reous remains. It appears formed, on the contrary, of extremely 

 minute particles of pure quartz, having an iiTegular foiTU and very 

 sharp angles. The dimensions of the gTains are much less than 

 those of other similar deposits : Thus, whilst the grains of sand 

 from the coast of the North Sea measure from 4-lOOOths to 

 12-lOOOths, and those of the tertiary beds, 8, 16, and 24-lOOOths, the 

 grains of sand from the great desert measure only from 1-lOOOth to 

 4-lOOOths of an inch. — The author of these observations considers 

 the Sahara sand as belonging to one of the most recent tertiary 

 formations. 



We will now turn our attention for a while to Palaeontology. — It 

 is not long since, that Professor Owen, from the examination of a 

 single bone, or rather of a double tooth belonging to the lower 

 jaw of an unknown animal, was bold enough to create a new genus 

 of extinct pachyderms to which he gave the name of Coryphodon, 

 — the tooth resembled somewhat that of a Tapir. The eminent 

 palaeontologist, M. Hebert, has since fuUy confirmed the generic 

 distinction so sagaciously established by the illustrious English 

 ♦ Compare Humboldt ; Views of Nature, Bohn's edition, 1850, p. 89. 



