Notices of Memoirs — Dr. W. MacMe — Fossil Water. 559 



Though the solution of ammonia and ammonium chloride in the 

 sandstones is no doubt very dilute, it is probably, as compared with 

 the solution of manganese in the infiltrating water, relatively strong. 



Presuming the access of oxygen — which may be taken for granted 

 in the case of porous rocks like sandstones — the explanation of 

 the precipitation of manganese dioxide simply resolves itself into 

 accounting for a preponderance of alkalinity at the special points of 

 precipitation of that substance. Analyses show that the manganese 

 areas contain excess of lime, magnesia, and alkalies, compared with 

 what obtains in the surrounding sandstones. This may have been 

 a cause of increased alkalinity, and hence of the precipitation of the 

 manganese dioxide. On the other hand, it may simply be a con- 

 comitant of the pi'ecipitation, and due to the same cause. The 

 alkalinity in some of the manifestations enumerated has undoubtedly 

 beendue to carbonate of lime, (1), (2), (4), (8), (9); to the ammonia 

 arising from the decomposition of organic remains, (1), (8), (9) ; 

 to the presence of carbonated alkalies, (3), (5), (6), (7) ; and to 

 free ammonia of the sandstone water after the total precipitation 

 of the ferric hydroxide in a higher zone of the sandstones, (7). 

 The conditions that are necessary for the precipitation of manganese 

 dioxide are the presence of alkali or alkaline substance in excess, 

 soluble manganese compounds in transit, and facility for oxygenation. 



There is nothing particularly unique in the precipitation of 

 manganese dioxide. It is simply an extension or continuation of 

 the same action as determines the precipitation of ferric hydroxide, 

 and a general separation is effected between the two substances 

 by the fact that the iron compounds fall out before the manganese 

 as the infiltrating water containing them encounters further and 

 farther supplies of alkali. The general distribution of the two 

 substances in the Elgin Sandstones illustrates this natural method 

 of separation, the rocks impregnated with secondary infiltration of 

 ferric hydroxide in a general way occurring in a zone overlying 

 those impregnated with manganese dioxide. 



In the author's opinion the manganese nodules of the deep-sea 

 deposits owe their origin to the operation of the same or similar causes. 



As a general summary it may be stated that the principles involved 

 in Weldon's process for the recovery of manganese were long 

 anticipated, and had long been in operation in Nature's processes 

 before Weldon's day. 



II. — The so-called 'Fossil' Water of SEDniENTARY Strata, as 



ILLUSTRATED BY THE SANDSTONES OF THE MORAY FiRTH BaSIN. 



By William Mackie, M.A., M.D.^ 



A SERIES of determinations of the soluble chlorides and sulphates 

 locked up in the interstices of the Elgin Sandstones, was made 

 to test the thesis that from such an examination it is possible to 

 determine the character, as to freshness or salinity, of the waters of 

 the basin of deposit of a series of sedimentary rocks. 



In the present case, though some interesting side issues were no 

 ' EeacI before the British Association, Belfast, Sept. 1902, in Section C (Geology). 



