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1'iscovery of coprolitic pellets of mud in a "red 

 clay," off the Isle of Arran in the Clyde marine basin. 



These pellets are casts, excreted by the creatures 

 which subsist by passing the mud through their bodies 136 



These animals are furnished with powerful tritu- 

 rating apparatus, or gizzards. 



Manganese ochres found in nearly all the seas round 

 the coast of Scotland. 



prolitic pellets found in great abundance off the 

 mouth of the river Congo, in the South Atlantic and in 

 all deep sea clays . . . . . . 137 



Ki markable blue clay, impregnated with sulphides, 

 found in the Sound of Jura, Scotland . . . .138 



Reducing action of organic matter recognized by 

 Bischof, and the efficacy of trituration in aiding the 

 decomposition of minerals shown by Daubree and 

 confirmed by the author . . . . . .139 



Chemical reaction between the minerals of the mud, 

 the sulphates in the sea-water and the organic secre- 

 tions of the animals, produces sulphides out of the 

 minerals, and these are transformed into oxides by the 

 oxygen in the sea-water. 



If this process takes place we should find traces of 

 sulphur in the ochreous deposits . . . .140 



A number of deposits were examined in this sense. 



Method of estimating the sulphur in the muds. 



Treatment of the mud with carbon bisulphide. 



Treatment with chloroform preferred. 



Greatest amount of sulphur found in the blue clay 

 from the Sound of Jura. It contained 0-4 per cent. . 141 

 ription of the muds analyzed . . . .142 



Table of analytical results % . . . . .144 



K i suit of the analyses: Sulphur was detected in 

 all the samples and was determined in the greater 

 number of them . . . . . . . .147 



Discussion of the chemistry of the reaction which 

 takes place in this metamorphosis of the deep-sea 

 deposits. 



It is a case of catalysis depending on the alternate 

 production and destruction of a trace of free arid . 148 



Illustrative experiments made with artificial ma- 

 terials, Manganese Sulphide, Ferric Chloride, and others 149 



C.rcat instability of sulphuretted muds when 

 exposed to the atmosphere . . . . .150 



