[325] 
XXIII. 
ON THE INNER MECHANISM OF SEDIMENTATION— 
(PRELIMINARY NOTE). By J. JOY, 8c. D., F.R.S., 
Hon. Sec. Royal Dublin Society, Professor of Geology and 
Mineralogy, Trinity College, Dublin. 
[Read Aprit 25; Received for Publication Aprin 27 ; 
Published June 30, 1900.] 
Ir has long been known that the presence of dissolved salts 
accelerates the precipitation of finely divided matter, such as 
clay, &¢c., suspended in water. The phenomenon has not, however, 
met the consideration which its extreme importance as a factor in 
geological physics claims for it. The entire distribution of marine 
sediment had been widely different from that which exists, and 
sediments transported from continent to continent and carried 
from the land into all parts of the ocean, but for the intervention 
of this effect. I propose in this brief note to summarise the 
results of an inquiry as to the nature of this phenomenon, upon 
which I have been engaged. 
I find that a large part of the work which has been done 
within recent years on the coagulation of colloids apples to 
the precipitating powers of salts. It will be found that some 
contradictory statements of previous observers (as to the ineffec- 
tiveness of sodium chloride to effect precipitation) find explanation 
in the facts forthcoming. 
It appears that the cessation of the phenomena of pedesis or 
Brownian movement is not concerned directly in producing 
precipitation, contrary to the idea of Jevons, but that the floccu- 
lation of the suspended particles attending precipitation and 
responsible for it, stops this motion, which, however, even then 
may continue to exist for free particles of sufficiently minute 
dimensions. The cessation of pedesis, therefore, does not primarily 
‘Thus the Gulf-stream cressing the Atlantic in about 100 days would have been 
competent to transport the finer suspensions from the American rivers to Europe. 
