VII. 
346 ALEXANDRIA. 
CHAP, hieroglyphics, cut to the depth of two inches into 
the stone, which consists of red granite ; but, 
owing to a partial decomposition of the fe/dspar, 
its red colour has faded towards the surface. 
A similar decomposition has frequently hastened 
the decay of other antient monuments ; and it 
offers proof of a fact worthy the notice of per- 
sons employed in national architecture ; namely, 
that granite is less calculated for works of 
duration, than pure homogeneous marble, or 
common limestone. The action of the atmo- 
sphere conduces to the hardness and durability 
of the two latter ; but it never fails to corrode 
and to decompose substances where feldspar is 
a constituent. Examples may be adduced of 
marble, after continual exposure to air and 
moisture during two thousand years, still re- 
taining the original polish upon its surface 
unaltered ; but granite, under similar circum- 
stances, has not only undergone alteration, but, 
in certain cases, has crumbled, and fallen into 
the form of gravel, owing to the decomposition 
of the feldspar. Instances of such disintegration 
may be noticed among the ruins of Alexandria 
Troas, and over all the district of Troas in 
general. Some of the granite columns used by 
the Turks in the fabrication of their cannon-balls 
have been found in such a state of decompo- 
