NO. 14.] MECHANICAL COMPOSITION OF SAMPLES. 15 



the Clay is found in the samples. In order to solve this question, it will be 

 necessary to subject it to a close investigation. 



All clays or kaolins are originally possessed of so extraordinary a fine- 

 ness that in the process of washing a large quantity will come out among 

 the constituents that are less than O'Ol mm. It is for instance a well-known 

 fact that the clay can be held suspended in fresh water for a very long time, 

 so that in kaolin-pits and brick-fields it is necessary to have very shallow, 

 flat reservoirs in order to get it separated from the water. This circumstance, 

 however, is modified in many ways, and the transition to salt water in the 

 first place, plays a very important part. It is also a fact that has often been 

 observed, that clay sinks to the bottom far more rapidly in salt water than 

 in fresh, although the former is not so fluid as the latter, and moreover has 

 a higher density. Thoulet 1 has pointed out that large particles sink at a 

 perceptibly slower rate in sea-water than in fresh, and that the proportion 

 between the velocities is about - 955. The density of sea-water is about 

 T0265 2 , and Thoulet, in his experiments, has employed a solution of NaCl 

 of this specific gravity. The proportion between the velocities of deposition 

 would be 0974, (the reciprocal of the above named 10265), if the density 

 alone determined the velocity of deposition. As the difference is, however, 

 greater, it shows that the smaller degree of fluidity in sea-water must be 

 of some consequence, and it would seem most natural to suppose that this 

 would be of still greater significance in the case of the finest particles. Here, 

 however, other circumstances assert themselves, and in order to come to a 

 clear understanding of them, I have made the following experiments. 3 



A sample of very fine clay was boiled thoroughly in distilled water, and 

 after being cooled down, an equal quantity of the liquid was poured into 3 

 glass cylinders of the same size and shape. One of these contained fresh 

 water, the second, water with 1 per mille NaCl, and the third water with 35 

 per mille NaCl, or about the same permillage as sea-water. I have not 

 investigated the question of the possible influence of the other salts in sea- 

 water, but they probably act in the same way as common salt, although in 



1 Analyse niecanique des sols sous-marins. Annates des Mines, April, 1900. 



2 Not in the Polar Sea, where it is 1-028. [F. N.] 



3 For further particulars see Atterberg: Stutlier i Jordanalysen. Landtbrnks-Akade- 

 miens Handlingar och Tidsskrift, Stockholm, 1903, p. 217 etc. 



