316 Mr. Napier on Sanditones used for Building. 



Silica and mica, 77*4 



Clay, 15-6 



Lince, 38 



Protoxide iron, 2'2 



Magnesia 1' 



100-0 

 After washing these are — 



Sand Washed. Clay Separated. 



Silica and Mica, 9-4-6 Clay, 88 6 



Protoxide iron, 1'2 Protox. iron,... 5'3 



Lime 3-8 Lime, 4 



Magnesia, -4 Magnesia, 2-1 



100-0 100-0 



All this lime is not from the mica, and shows that lime adheres to the 

 quartz with great force, and gives cause for suspecting that the clay 

 may have a tendency to prevent the proper binding of the quartz par- 

 ticles ; and this idea is somewhat borne out by the statement made by 

 the Commissioners appointed to inquire into building stones for the 

 New Houses of Parliament. They say in reference to Edinburgh : — 



'' 3Iodern buildings erected from the Craigleith quarry, none of them 

 exhibit any appearance of decomposition, with the exception of ferruginous 

 stains which are produced upon some stones. Amongst the oldest is the 

 Ptegistry Office, which is of Craigleith, and built above 60 years since : it 

 is in a perfect state." 



Now in turning to the analysis given of this stone by the late Professor 

 Daniell at the time the Commissioners made their inquiry, it stands as 

 under : — 



Silica, 98-3 



Lime, 1-1 



Iron and alumina, -6 



100-0 



Here we have no clay mentioned, and although the quantity of lime is 

 very small, still as nothing intervened it may have formed a perfect 

 cement along with the iron present. And we may here mention, while 

 treating of this particular stone, that the Craigleith quarry seems to 

 produce a different quality now than it did 14 years ago, when the above 

 analysis was made, that stone, according to the specimen I have from 

 Craigleith, has almost none of the characters of a sandstone; it is more 

 compact than granular, and has a vitreous crystalline appearance, and 

 possesses every character of a lasting stone. Its composition is nearly as 

 under : — 



