i 
ON THE MARGIN OF LOCH LOMOND. 337 
A little attention may be necessary, to an opinion, which 
'we sometimes hear expressed in conversation, " that such 
hollows, as Loch Lomond, with a bottom so far below the 
level of the ocean, ought, if ever they were filled by it, still 
to retain its salt water.*" It seems to be imagined, that the 
sea- water, on account of its greater specific gravity, is still 
retained in the deep pits of these chasms, and that the 
fresh-water glides unmixed above it, or changes by evapo- 
ration and renewal, without affecting its deeply buried mass. 
It does not seem difficult to demonstrate the improbabihty 
of this supposition. For the phenomena of solution can be 
accounted for only on some hypothesis such as this : that, 
when a film of pure water is applied to a film containing 
salt in solution, there is a tendency in them to unite, and 
form a compound of less saturation than the latter ; which 
compound has a corresponding influence on the nearest, or 
on any number of saturated films beneath it ; and will, in 
like manner, be affected and changed by the next pure 
film above it, and, successively, by any number of films in 
any depth of water. The changes will cease only when an 
equilibrium of attractions has taken place through the whole 
mass, which will then be in a state of medium and uniform 
saturation. Whatever be the time required for the com- 
bination of two films, that time would be an element in the 
equation, representing the whole period necessary to pro- 
duce uniformity, which must therefore depend on the num- 
ber of films, or be a function of the depth. Changes of 
temperature at the surface would very much accelerate the 
result, by sending downwards dense films, having the high- 
est degree of attraction, until stopt among others, having 
the same specific gravity, arising from greater saturation ; 
so that probably no long time would elapse before nearly 
uniform saturation took place, even though the combined 
depth of the fluids were considerable. But the tendency 
