138 Generation of Sulphur in 



complete disappearance on drying. It is worthy .of more 

 particular mention. 



On 6th July 1879 tne anchor dredge was put over in the 

 Sound of Jura, where a depth of 120 fathoms was marked 

 on the chart. It did not hold, and the yacht drifted, dragging 

 it over the ground in a northerly direction before the wind 

 and tide. Suddenly it hooked the ground, and brought the 

 vessel up with a great strain on the cable. In heaving up 

 it was with difficulty that the anchor was broken out of the 

 ground; and when it was brought to the surface the bag 

 was full of a fine, unctuous, very tenacious blue clay, with 

 some of the reddish-brown surface mud covering it. There 

 were a few pieces of broken shell and rock, also smooth and 

 rounded pebbles, which seemed to occur principally in the 

 part separating the surface mud from the blue clay, but there 

 was very little of this kind of matter. The whole bagful, 

 weighing more than i cwt., consisted almost entirely of 

 homogeneous blue clay of a tenacity similar to the clay dug 

 for brickmaking, and quite different from ordinary "blue 

 muds." The clay was rather foul-smelling, and gave off 

 abundance of sulphuretted hydrogen when treated with hydro- 

 chloric acid. It was so tenacious that it was impossible to 

 break it up in water for the purpose of levigation, which is 

 always very easily accomplished with ordinary muds. A con- 

 siderable portion of it was dried and taken for analysis. It 

 was found that, as soon as dry, not a trace of sulphide was 

 to be found; but the mass of the clay was permeated with 

 fine particles of oxide of iron, each of which represented a 

 previous particle of sulphide. The contrast between the fresh 

 moist clay, which was thoroughly impregnated with sulphides, 

 and the dried clay, without a trace of them, was very 

 striking 1 . 



The fact then had been demonstrated that the mud is 

 being continually passed and re-passed through the bodies of 



1 A condensed account of my views of the part played by the sulphates 

 of the sea water in the production of the ochreous deposits on the bottom 

 of the ocean, and of the carbonate of lime of the shells of the Mollusca, 

 is published in the Reports of the British Association (York), 1881, p. 584. 



