Mr. Watt’s Observations 
296 
them in its turn. From the same consideration it is obvious, 
that no crystal can be formed at a temperature above the degree 
of its fusibility ; and that, as a necessary consequence, no crystal 
■which is more fusible than the basis in which it is imbedded, can 
be formed by igneous operation. 
The same laws must regulate the arrangement of aqueous 
solutions, and of molecules suspended in aqueous solutions. All 
these are dependant on heat ; for we are unacquainted with any 
fluidity, and consequently with any solution, which heat does 
not produce. Ice and soda have no more action on each other 
than soda and quartz : raise the temperature of the ice, and it 
unites with the soda ; raise the temperature of the soda, and it 
unites with the quartz. Both solutions are effected by heat, of 
the degrees of which we know neither the beginning nor the 
end r and are therefore utterly unable to estimate what aliquot 
part of its scale is adequate to the production of these effects. 
Probably a very minute one. 
A curious diversity may prevail in the products of a com- 
pound body subjected to fusion, when absolute solution is pro- 
duced. When merely simple fusion takes place, the aggregation 
of the parts only is destroyed: the fluidity arises from the 
facility with which they move on each other ; and a regulated 
diminution of temperature, by facilitating their reunion, can 
hardly fail to recompose the same species that formerly appeared 
to exist in the compound. But, if the molecules have been dis- 
solved and decomposed, and their component particles diffused 
through the fluid, there seems to be very little probability that 
any reunion should compose the same molecules. It is more 
likely that new compounds will be formed, from which new 
molecules, and of course new crystals, will be generated ; and 
