THE GEOLOGIST. 
3S 
author that the phenomena to which we have just alluded remind 
us of the instability of the present order of things, and the changes 
to which the outlines and configurations of continents are probably 
still subject at long intervals of time. 
Our distinguished friend. Dr. Van den Corput, during a recent 
travel in Africa, has paid particular attention to the sand of tlie 
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, i e., a 
superficies nearly three times that of the Mediterranean.* This 
sand is so white and of so fine a grain, that one could easily 
mistake it for pulverized glass. — Ehrenberg once professed the 
opinion that the sand of Sahara was chiefly formed 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 irregular form and very 
sharp angles. The dimensions of the grains 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 24-1000ths,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 fully confirmed the generic 
distinction so sagaciously established by the illustrious English 
♦ Cgmpare Humboldt : Views of Natui'e, Bohu's edition, 1850, p. 89. 
