Sxry.—Osomose, as the Cause of Suspension of Clay in Water. 489 
There is, perhaps, one point in respect to this, about which you may 
require further information ere you would be prepared to give an opinion 
respecting the accuracy of my theory. It may be asked whether, in all 
instances of persistent clay diffusion, there is sufficient soluble saline matter 
present of such a nature, and which is, besides, so unevenly distributed, as 
to enable dialysis to be carried on to the necessary extent ? 
In regard to this, I would reiterate the statement which I have made, 
that dialysis is best produced by very weak saline solution, and I would, 
besides, remind you that by far the most effective solutions for this purpose 
are those of the alkalies, and it is precisely matter of this kind, which, as it 
happens, is certain to be present and unequally distributed in any clay 
water we may ever prepare. 
In all clay, as you are aware, some alkaline matter is present, and in 
such a form that it gradually passes into solution. Again, ammonia 
can, as we know, scarcely be excluded from the water through which clay 
may be diffused, and it signifies not where the alkalies are, whether with 
the clay or the water, so long as they are not equally diffused throughout 
both. 
In this connection it is proper to note the fact which has been recently 
discovered * :— That the power which water possesses of sustaining clay in 
suspension is increased by the addition of small quantities of the alkalies or 
their carbonates,” and that water, whose power of sustaining clay had been 
destroyed by an acid, had this power restored in great measure by any of 
the alkalies. Now precisely the same kind of thing would happen in the 
case of albumen, and conversely salts in large quantity retard or prevent 
the alkalies acting in this manner. The analogy therefore between clay and 
albumen in respect to my subject, is obviously of so wide and general a 
character that we may safely assume them to be alike capable of assisting 
in osomotic action and its results. 
In conclusion, I would state that I have thus singled out the persistent 
suspension of clay for explanation in place of the persistent suspension of 
substances of a like nature generally, because the question of clay suspen- 
sion is to me of particular interest as being one I have had in my mind for 
a long time past, and I obtained by experiment results thereon which I am 
persuaded are of some value in regard to its settlement. 
Granted, however, that this attempt of mine at the explanation of the 
persistent suspension of clay is a successful one, the principle thus involved 
„is so easy to make a general application of, to the explanation of those 
* Suspension of Clay in Water, by William Durham, F.R.S.E. Read before the 
Physical Society of Edinburgh, 28th January, 1874. F^ 
