1889.] Barium Sulphate as a Cement in Sandstone. 



after examining at my request a number of specimens in his possession, 

 f mud in one of them a small quantity of barium, entirely in the 

 form of carbonate. This specimen was taken from the rock of Beeston 

 Castle Hill, Cheshire, from Keuper basement beds, of the same 

 formation, therefore, as those in which the sulphate has been found 

 in this neighbourhood. In the geology of the neighbourhood of 

 Chester (' Greol. Survey Memoirs,' 1882, pp. 7, 8), Mr. Aubrey 

 Strahan, M.A., states that barium sulphate occurs in cracks in the 

 rock of Beeston Castle : and further infers that the sulphate may 

 exist as a cementing material, since the cemeut gives a sulphur reac- 

 tion with the blowpipe. The presence of the sulphate in cracks of the 

 stoue is similar to its presence in crystal tufts in the cracks of the 

 septaria of the London clay, which has been long known. The occur- 

 rence of the sulphate over a large area in the Nottingham district, 

 as well as in Cheshire, seems to indicate that the substance may be 

 characteristic of the particular formation in which it occurs in both 

 localities, namely the Keuper basement beds. 



On the Continent the occurrence of barium sulphate, under con- 

 ditions more or less similar to those recorded above, has been 

 recorded by Bischof (' Chem. and Phys. Geology,' vol. 1, p. 433). 

 Sandstone cemented by barium sulphate, was found by him in 

 Miinzenberg, in the Witterau. He also describes disintegrated 

 granite as being found cemented by the sulphate on the declivities 

 of the Morvan;. and sand and clay were found compacted by the 

 sulphate in the district of Keuznach. 



Process of Deposition. 



There seems little to indicate the way in which the nearly insoluble 

 sulphate has been deposited in the sand in the c ise under considera- 

 tion. There is the possibility of barium sulphide in solution becoming 

 insoluble by oxidation, as suggested by Professor Church ; or the 

 sulphate itself may exist in solution under conditions at present 

 unknown, and be deposited directly from its solution. 



The fact that calcium sulphate was detected in some specimens of 

 the sandstone which I examined, and that barium carbonate was 

 found in similar beds in Cheshire, lends probability, however, to the 

 formation of the sulphate by double decomposition. Bischof (loc. cit.) 

 describes experiments in which solid barium carbonate, as well as 

 barium bicarbonate or barium silicate in solution, were readily con- 

 verted into barium sulphate by the action of any soluble sulphate, 

 such as the sulphate of calcium or of magnesium. And Haidinger 

 (Poggendorff's ' Annalen,' vol. 11, p. 376) has traced the change in 

 progress in nature; barium carbonate present in mountain limestone 

 of Alston Moor being found by him undergoing slow conversion from 



vol. xlvi. 2 c 



