ARCHlTECTUREi 
859 
Ven decay the first ; oiling and painting will only re* 
tard the destruction ; and stones which resist all 
Watery agency, and refuse to burst with changes of 
temperature, are secretly eaten away by the chem-' 
ical forces of carbonic acid and other atmospheric 
influences." The same writer remarks, " There is 
no doubt that very great benefit would result to the 
building art if the whole kingdom were surveyed 
by geologists and architects, for the purpose of de-» 
termining generally the occurrence and qualities of 
stone suited for great and costly edifices." In ac- 
cordance with this suggestion, a commission was 
issued by the British Parliament^ appointing the able 
geologist, Mr. De la Beche, and an architect, to se* 
lect for the new houses of Parliament the best ma- 
terial for this national workj and they have already 
reported. It is hoped that this example may not 
wholly be lost to this country. 
A very good mode of judging of the durability of 
rocks is to observe the effects of the atmospheric 
influences in the locality whence the rock is ob- 
tained. Its appearance, especially if it be a com* 
pound rock) will readily indicate whether it is easi* 
ly acted upon by these causes, or the reverse. Foi* 
example, if the rock be a granite, and it be very 
uneven and rough, it may be inferred that it is not 
durable ; that the feldspar, which forms one of its 
component parts, is more readily decomposed by 
the action of moisture and frost than the quartz, 
which is another ingredient ; and, therefore, that it 
is very unsuitable for building purposes. Mofe* 
over, if it possess an iron-brown or rusty appear- 
ance, it may be set down as highly perishable, ow- 
ing to the attraction which this metal has for oxy- 
gen, causing the rock to increase in bulk, and so dis- 
integrate* This may be seen in much of the gran- 
ite which is quarried in the Eastern States, but not 
in all. The syenitic granites of Quincy and other 
places, which contain a very compact species of 
