1853.] Report on the Geological Structure of the Salt Bang e. 255 



The grey sandstone when treated with muriatic acid, dissolves 

 slowly with effervescence, leaving a considerable residue of a nearly 

 white silicious sand. On filtering this from the acid solution and 

 applying to it the usual tests, lime and magnesia were found in 

 abundance with a trace of protoxide of iron and alumina. The rock 

 under notice is therefore a sandstone, the cementing agents being 

 carbonate of lime and magnesia. Sometimes the two latter largely 

 predominate, and give the sandstone more of the character of a 

 coarse limestone. In a few of its beds, the cementing ingredient 

 seems to be entirely carbonate of lime, and the examination of a 

 specimen from one of these bands obtained at Baghanwala in 1848, 

 which did not yield a trace of magnesia, led us to believe that this 

 earth was not characteristic of the formation, which its appearance 

 induced us to suspect. 



A specimen of this sandstone from Mount Tillah yielded on analy- 

 sis, the following results in 100 parts. 



"White quartz sand, 28.000 



Carbonate of iron with a trace of alumina, 7.3 13 



Carbonate of lime, 32.874 



Carbonate of magnesia, 31.199 



Loss, 614 



Total, ... 100.000 



This sandstone or coarse magnesian limestone will, we are assured, 

 be found to be most excellent and durable building stone, and it is 

 much to be regretted, that it was not selected for the construction 

 of the obelisk in the Chillianwalla burial-ground, the red sandstone 

 of Pind Dadun Khan having been preferred. Though rather hard, 

 it is easily worked, and when roughly polished, is highly ornamental 

 from its possessing a semi-crystalline structure. 



It may be had in abundance on mount Tillah, the summit of which 

 it forms, and all along the Salt Eange from Jelalpur to Mukrach, to 

 the West of which place it gradually thins out in the micaceous 

 green sandstone. 



Like most calcarious rocks, it is liable to be acted on by water 

 charged with carbonic acid, and hence along the upper weathered 



2 k 2 



