318 5Ir. Nai'IEK on Sandstones used/or Building. 



In the above table no notice is taken of sulphur. I Lave often found 

 traces of sulphur in the ordinary stone, and in particular pieces of stone 

 a considerable quantity, but I have not in general found it in such pro- 

 portion as to make me suspect it having anything to do with the destruc- 

 tion of the stone, being a mere trace in 100 grains. Sulphuret of iron 

 in the stone might cause decay by efflorescence, but I have generally 

 found the iron to exist as a carbonate. 



The application of these analyses to useful purposes, or to the wearing 

 quality of a stone, is as yet unknown to me, owing to the want of data. 

 I was, however, kindly supplied by a builder with four specimens, from a 

 house he was taking down. Two of these were from stones that had 

 coiToded very much, the other two had stood the wear well, all having 

 been placed under the same circumstances for upwards of 20 years. 



The first sample tried has not corroded all over, but in lines, forming 

 deep ruts or furrows in the stone. This gave by analysis — 



Silica and mica, 73-6 



Clay, 22-0 



Peroxide iron, 2-8 



Lime, 1-2 



lesia, trace. 



99-6 

 No. 2 had corroded all over, mouldering into sand. It gave- 



Silica and mica, 770 



Clay, 200 



Peroxide iron, 1'4 



Lime, 1'6 



sia, trace. 



lOO-O 



No. 3 stood well, and was a slight reddish colour. It gave — 



Silica and mica, 90'2 



Clay, 6-8 



Lime, 2-2 



Peroxide iron, -8 



100-0 



No. 4 stood well, was white, gave — 



Silica and mica, 89.2 



Clay, 8-3 



Lime, 1-8 



Peroxide iron, -4 



99-7 



