130 Beviewa — J. Joly's Age of the Earth. 



consolidated. And it is distinctly salt to the taste. On submitting 

 a fragment of this rock for examination to Mr. Purvis, of the 

 Cambridge University chemical laboratory, he found that it contained 

 G'568 of soluble matter, of which 0-04:2 per cent, consisted of chlorine 

 calculated to sodium chloride. Now the specific gravity of this rock 

 is 2-59. Consequently, since a cubic foot of water weighs 1,000 

 aunces, there are 1*08 ounces of chlorides in a cubic foot of the rock 

 and 2-27 ounces of other soluble salts. In like manner a piece of 

 Devonian shale from Meux Brewery in Tottenham Court Eoad at 

 the depth of 1,070 feet was found to yield I'll per cent, soluble in 

 water, but the amount of chlorine was too small to determine. 



It is interesting to compare these old rocks with such as we might 

 suppose would now be forming. Accordingly it was found upon 

 squeezing dry some mud from Southampton Water that the matter 

 soluble in water was 0495 per cent., and of " chlorine calculated to 

 sodium chloride 0-074 per cent." This mud was derived from 

 Middle Bracklesham sands, and yielded a soft sandstone rock when 

 consolidated in a hydraulic press. 



Some mud from the Fleet near Weymouth, when treated in the 

 same manner, yielded 0-9 per cent, of soluble matter, of which 

 chlorine calculated to sodium chloride gave 0-29 per cent. 



It is remarkable that the total amount soluble in these hypothetical 

 recent rocks is closely analogous to that in the ancient rocks 

 examined, and also that the proportion of sodium chloride in both 

 cases is comparatively small ; whereas in sea-water it is very much 

 greater than that of any other salt. Mr. Purvis adds : "This pressed 

 mud also contains probably mixed sulphates, such as magnesium 

 sulphate, sodium sulphate, potassium sulphate, and calcium sulphate." 

 It is natural to conclude that the decomposition of iron sulphide in 

 the original sands may have converted much of the chloride into 

 sulphate. Sulphuric acid is also a product of the combustion of 

 coal, which would account for the presence of a certain amount in 

 localities like those from which these muds were obtained. But 

 the point of interest is the probable substitution of sulphates for 

 chlorides, from whatever source the acid may have come. This 

 consideration shows that there may have been originally more sea 

 salt in a sedimentary rock than is indicated by the quantity of 

 sodium chloride it now contains. 



Another point to be noticed is, that the amount of salts in the 

 ancient rocks being so near that in rocks now presumably being 

 deposited, shows that the ocean was about as salt then as it is now, 

 and consequently not much additional sodium can have accumulated 

 in it during the long ages since Silurian times. 



In the 18th annual report of the U.S.A. Geological Survey • 

 •upwards of sixty analyses of well waters are recorded in Indiana 

 and Ohio. In the artesian wells sodium chloride is very abundant, 

 to the amount of 1,000 to 3,000 grains to the U.S.A. gallon. These 

 waters appear to be found in sedimentary rocks. In the 19th report^ 



1 1896-7, pt. iv, p. 500. 



2 1897-8, p. 650, "Kock Waters of OVo." 



