16 0. B. B0GGILD. BOTTOM DEPOSITS. [norw. pol. EXP. 



a different degree. I then, in the various experiments, poured different 

 quantities of the washed clay into the glasses, but exactly the same quantity 

 in each of the three glasses, each time. It then appears that if the quantity 

 of clay is so great as to make the water quite opaque in a glass with a diameter 

 of 1*5 cm., there is a marked difference in the rates of deposition in the 3 

 glasses. During the first few minutes, no difference is to be observed; but 

 at the expiration of half an hour, it will be seen that the water containing 

 the greatest amount of salt has become almost clear, the slightly saline water 

 is almost clear in the upper part and perceptibly clearer below, while in the 

 fresh water only the uppermost layer shows a slight indication of a decrease 

 in the quantity of clay, the greater part being apparently entirely unaltered. 

 After the expiration of twenty-four hours the water containing most salt is 

 quite clear, and the slightly saline water has only a very little clay floating 

 in it, while the fresh water still contains so much, that for the greater part 

 of its height it is quite thick, and it only becomes quite clear after several 

 weeks. If, however, we observe the clay in 3 glasses, both during deposition 

 and after, it will present a very different appearance in the different cases. 

 In the fresh water, it is always exceedingly finely and evenly distributed, 

 while in the salt water it coagulates, and after being deposited has an 

 uneven, gritty appearance. Thus the effect of the salt is to cause the separate 

 fine particles of clay to unite, and so in a manner alters the size of the grains. 

 This is confirmed still further by the phenomena exhibited when the clay is 

 in the form of a much diluted emulsion. It then appears that the differences 

 between the action of the several kinds of water are much smaller. If we put 

 into the glasses no more clay than is necessarv for a fairly clear observation of 

 the deposition, no noticeable difference is perceptible in the 3 glasses for the first 

 half-hour; indeed it almost appears as if the fresh water were a little clearer 

 at the very top than the salt. After the lapse of a few hours, however, we 

 shall nevertheless see that the salt water has become almost clear throughout, 

 while the fresh has scarcely made any progress in that direction. This seems 

 then to indicate that at first the particles of clay are at so great a distance 

 from one another that during the first part of the time they are unable to 

 unite to any great extent, and the fresh water's greater rapidity of depo- 

 sition can thus actually make itself apparent; but a union nevertheless 



