﻿436 DE. G. T. MOODY ON THE CAUSES OE [Aug. I905, 



Wight, there are at the present time enormous volumes of sub- 

 terranean chalybeate waters which contain either ferrous sulphate 

 or ferrous bicarbonate, but usually the latter. 



An artificial chalybeate water-ferrous bicarbonate solution was 

 prepared by placing soft iron-wire and water in a ' sparklet '- 

 syphon and then aerating with a ' sparklet.' After twelve hours 

 the solution gave all the characteristic reactions of a strong natural 

 chalybeate water. It had an inky taste, and, when boiled, yielded a 

 greenish-white precipitate of ferrous carbonate which rapidly turned 

 brown on exposure to air. Solutions of iron prepared in this way 

 contained as much as 0*3 gramme of iron per litre. 



The artificial chalybeate water, when forced by pressure of carbonic- 

 acid gas through a mixture of sand and chalk, was found to give up 

 the whole of its iron, calcium-bicarbonate passing into solution. 

 The substitution of magnesite, dolomite, and green marl for the sand 

 and chalk led to precisely-similar results, the effluent water being 

 free from iron, but containing calcium- or magnesium-bicarbonate. 

 On exposure to air, the masses holding the precipitated iron assumed 

 a red or brown colour. 



In the case of a rock containing both magnesium-carbonate and 

 calcium-carbonate, it was found that chalybeate water most readily 

 exchanged iron for magnesium. When the water was passed 

 through a long column of powdered dolomite, the effluent at first 

 contained only magnesium-bicarbonate ; and it was not until a 

 relatively-large volume of the water had passed through the rock, 

 that calcium-bicarbonate could be detected in the solution. 



It appeared of interest to convert part of the green portion of 

 some variegated marl artificially into red marl, and to compare the 

 colour and composition with the naturally-occurring red part. To 

 this end a stream of chalybeate water was passed through a finely- 

 divided green portion of marl for several hours. The product was 

 then spread on a plate and dried in an air-oven, when it was found 

 not only to match nearly in colour the naturally-red part, but also 

 to resemble it closely in chemical composition, as shown by the 

 following numbers : — 





N, 



VTURAL. 



Artificiai 





Green marl. 





Bed marl. 



Bed marl. 



Fe 3 



0-87 





3-80 



4-96 



FeO 



0-96 





0-91 



061 



CaO 



7-37 





518 



492 



MgO 



610 





542 



4-77 



co 2 



13-01 





10-21 



9-61 



Undetermined 



71-69 





74-48 



7513 



10000 10000 10000 



The ease with which iron is deposited from solution, in exchange 

 for calcium and magnesium, affords strong evidence in favour of the 

 view that variegation in rocks has in many cases resulted 

 primarily from the passage of chalybeate water through 



