84 THE CHEMISTRY OF CREATION. 



mountain-torrents to a distance from its original 

 position. Its great weight and density render it 

 easily separable, simply by washing, which carries 

 away the lighter particles of sand and mud, leav- 

 ing the heavy metal behind. 



In Egypt, the student of the chemistry of 

 nature is presented with a highly remarkable 

 illustration of the operation of these causes of 

 waste and decay. In countries where the atmo- 

 sphere is charged with moisture, and rain is 

 frequent, or wind prevalent, the destructive 

 effects of these agents upon the strongest build- 

 ings soon become evident. This is strikingly 

 exemplified in the Delta and the rest of Lower 

 Egypt, which are affected by the exhalations 

 arising from the neighbouring sea. The conse- 

 quence is, that Memphis, which was formerly 

 the celebrated capital of the whole kingdom, 

 Heliopolis, Sais, and other important cities, are 

 now mere heaps of ruins. The granite obelisks 

 at Alexandria are partly illegible through the 

 corroding influence of the atmosphere. On the 

 contrary, in Upper Egypt, the monuments, un- 

 affected by the inundations of the Nile, and 

 the tombs, exhibit no signs of decay after the 

 lapse of many centuries. The black bricks 

 made out of the mud of the Nile, and dried in 

 the sun, some of which have been exposed to 

 the open air for thousands of years, as is proved 



