03 CLAY SUSPENDED IN WATER. 133 



a given time. If particles put into heated water were not of the 

 same temperature as the water, the gases would be driven off from 

 them, and their place would be taken, on cooling, by water, which 

 would hasten the deposition. He asked whether, in the case of the 

 solutions, the difference of the specific gravity of the fluids might not 

 somewhat similarly affect the air entangled in the particles. 



Prof. Maskelyne said that he thought this paper was hardly suited 

 to the Geological Society, the question discussed in it being a purely 

 physical one. Absolutely pure water is viscous; and judging by 

 the influence of salts in solution in aiding precipitation and nitration 

 in the laboratory, it would seem that this viscosity is impaired by 

 salts dissolved in it. The results obtained might therefore be duo to 

 the different viscosities of the solutions employed. 



Prof Kamsay remarked that at any rate the fact remained that 

 the mud went down faster in salt water than in fresh ; and that 

 fact seemed to him to have important geological bearings. 



Mr. Evans expressed a hope that these experiments might be 

 carried still further, as, although they were undoubtedly of a phy- 

 sical nature, their results appeared to be of considerable importance 

 from a geological point of view. He suggested that experiments 

 might be made with solutions which, having been already saturated 

 with one salt, would yet dissolvo another without undergoing any 

 change of volume. 



Mr. D. Forbes stated that the authors results seemed to him to 

 be deserving of great confidence; his experiments had evidently 

 been conducted with all due care. 



Prof. Morris remarked that the subject was not a new one. 

 Mr. D. Eobertson studied it in 1873, and found that mud is less 

 rapidly precipitated in weak than in strong saline solutions. The spe- 

 cific gravity of the matter in suspension must also be taken into 

 consideration in such experiments. 



The President (Prof. Duncan) did not feel quite sure that the results 

 embodied in this paper would be found to have much practical bearing 

 on geological questions. Very fine sediments take a long time to fall, 

 and would probably be carried far out to sea. From his own 

 observations he did not think that the greatest quantity of mud was 

 precipitated at the mouths of rivers. 



