74 Rev. J. Adamson on the 



be necessary to an opinion which we sometimes hear ex- 

 pressed in conversation, *' That such hollows as Loch Lo- 

 mond, 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 ac- 

 count 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 evaporation and renewal, 

 without affecting its deeply buried mass. It does not seem 

 difficult to demonstrate the improbability of this supposition. 

 For the phenomena of solution can be accounted for only on 

 some hypothesis such as this, — that where 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 corre- 

 sponding influence on the nearest, or any number of satu^ 

 rated films beneath it, and will, in like manner, be aff'ected 

 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 ta^- 

 ken place through the whole mass, which will then be in a 

 state of medium and uniform saturation. Whatever be the 

 time required for the combination of two films, that time 

 would be an element in the equation, representing the whole 

 period necessary to produce uniformity, which must, there- 

 fore, depend on the number of films, or be a function of the 

 depth. Changes of temperature at the surface would very 

 much accelerate the result, by sending downward dense films, 

 having the highest degree of attraction, until stopped among 

 others having the same specific gravity, arising from greater 

 saturation ; so that, probably, no long time would elapse be- 

 fore nearly uniform saturation took place, even though the 

 combined depths of the fluids were considerable. But the 

 tendency towards uniform saturation is opposed in a manner 

 which must quickly draw off the salt-water from a hollow, 

 such as a lake, because the surface water, in general, is con- 

 tinually changing, and the water which has become slightly 

 saturated flows off, and is replaced by that which is purer, 

 and has a greater attraction for the salt ; and to satisfy this, 



