340 Baron Cuvier's Lectures on the Natural Sciences. 



resi>onded to the same sideral epochs as at the time when they 

 were instituted — and that, to return to them, they required to 

 pass through all the seasons in succession. This period, at the 

 end of whicli every thing was restored to the original order, 

 was what the Egyptians named the Great Year, or the Year of 

 Syrius. 



It is probable that it was only from the heliacal rising and 

 setting of the principal stars that the Egyptians succeeded in 

 thus approximatively determining the length of the year ; for 

 their means of observation were very imperfect, and it is not 

 believed that they had any other instrument than the gnomon 

 for measuring the heights of the sun. 



We might be inclined to think that the Egyptians were very 

 little advanced in general physics, were it true that they con- 

 sidered fire as an animal which devoured the bodies that were 

 presented to it ; but, perhaps, this was only the opinion of the 

 vulgar, and not that of the learned. 



The Egyptians had very correct ideas on several points in 

 geology ; they had well observed the laws of alluvial deposition, 

 and at the present day we account for the formation of the Delta 

 in no other manner than that in which it was accounted for in 

 the days of Herodotus. They had discovered the existence of 

 solids not only in the alluvial formations, but also in rocks. 

 Thus, it may be thought, that when Thales in Greece declared 

 water to be the first principle of all things, he only gave a new 

 form to the theories of the Egyptian priests, who alleged that 

 the earth had arisen from the waters. 



The properties of minerals were tolerably well examined. 

 The country offered every facility for this ; the mountains 

 which form the sides of the valley of the Nile exhibited, and 

 in all their native lustre, various species of rocks ; in the lower 

 part limestone, farther up sandstone, and towards Syene por- 

 phyry and granite. Egypt was in some measure a great mi- 

 neralogical cabinet. The necessity of passing along the small 

 valleys which run towards the Red Sea, led to the discovery 

 of other minerals which do not occur in so great masses. It was 

 in one of them that the mine of emeralds was discovered, which 

 supplied all those known to antiquity. 



The manner in which the Egyptians wrought fine stones, por- 



