1878.] 
Suspended in Liquids. 
1 77 
powders prior to those which I made in 1869, the results of 
which were briefly published in the “ Proceedings of the 
Manchester Literary and Philosophical Society” for January 
25th, 1870 (vol. ix., p. 78). Since then several experimenters 
have treated the subject. Mr. Wm. Durham, F.R.S.E.,* 
has correctly apprehended that the suspension depends upon 
the non-condudting nature of the fluid ; but he is evidently 
wrong in supposing that the electricity is generated by the 
falling of the particles through the fluid, inasmuch as the 
pedetic movement, which favours suspension, is greatest 
when the falling of the particles is slowest. Mr. David 
Robertson has tested the precipitating power of salt, or even 
slightly brackish water, t and Mr. Wm. Ramsay, principal 
assistant in the Glasgow University Laboratory, has at- 
tempted an explanation of the fad with which I cannot 
agree.J He attributes the varying rapidity of the settling of 
clay suspended in saline solutions to the varying absorption 
of heat by the solutions, whatever this may mean. 
In the “ Chemical News ” for August 31, 1874 (vol. xxx., 
p. 97) it was pointed out that Dr. Sterry Hunt read a paper 
before the Boston Society of Natural History, on February 
18th, 1874, in which he alluded to the rate of settlement of 
clay in the water of the Mississippi River. The suspended 
matter, chiefly clay, amounts to about 1 part in 2000 parts of 
the water, and takes from ten to fourteen days to subside. 
But he observed that additions of sea-water, salt of mag- 
nesium sulphate, alum, or sulphuric acid, rendered the 
turbid water clear in twelve or eighteen hours. Fie thus 
explained the ready precipitation of the suspended clay 
when the river-water comes into contact with the salt water 
of the Gulf of Mexico, causing great deposits of fine mud, 
and helping 11s to understand the origin of the accumulation 
of clay slates in various geological formations. My experi- 
ments in 1869, and since, entirely confirm these observations 
of Dr. Hunt, and lead me to think that the pedetic move- 
ment must have played a most important part in geological 
processes. 
The power of salts to precipitate suspended particles has 
long been known practically. In some parts of the world 
* Abstract of a Paper read before the Royal Physical Society of Edinburgh, 
January 28th, 1874 (Chemical News, August 7th, 1874, vol. xxx., p. 57). 
t “ Note on the Precipitation of Clay in Fresh and Salt Water.” — Trans- 
actions of the Geological Society of Glasgow, vol. iv., p. 257. See Whitaker’s 
excellent Geological Record for 1874, p. 182. I have not been able to refer to 
the original paper. 
+ Abstract of the Proceedings of the Geological Society of London, No. 21s, 
March 8th, 1876, p. 1. 
VOL. VIII. (N.S.) 
N 
