Note vi. § 13.
Mr Kirwan's notion of precipitation.
162. The Neptunist who has provided the means of dissolving the materials of the strata, has only performed half his work, and must find it a task of equal difficulty to force this powerful menstruum to part with its solution. Mr Kirwan, aware in some degree of this difficulty, has attempted to obviate it in a very singular way. First, he ascribes the solution of all substances in water, or in what he calls the chaotic fluid, to their being finely pulverised, or created in a state of the most minute division. Next, as to the deposition, the solvent being, as he acknowledges, very insufficient in quantity, the precipitation took place, (he says,) on that account the more rapidly.
If he means by this to say, that a precipitation without solution would take place the sooner the more inadequate the menstruum was to dissolve the whole, the proposition may be true; but will be of no use to explain the crystallization of minerals, (the very object he has in view,) because to crystallization, it is not a bare subsidence of particles suspended in a fluid, but it is a passage from chemical solution to non-solution, or insolubility, that is required.
If, on the other hand, he means to say, that the solution actually took place more quickly, and was more immediately followed by precipitation, because the quantity of the menstruum was insufficient, this is to assert, that the weaker the cause, the more instantaneous will be its effect.
Of two propositions the one of which is nugatory, and the other absurd, it is not material to inquire which the author had in view.