ARCHITECTURE. 



359 



ten 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 work, 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. For 

 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. More- 

 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 



