3 °° 
Mr. Watt’s Observations 
I have endeavoured to show, that in the crystallizations re- 
sulting from igneous fusion, it is not only possible but probable, 
that the most infusible substances might not be the first to 
crystallize ; and this appears to involve important consequences, 
for it partly removes one of the greatest difficulties that embar- 
rasses the igneous theory, by explaining the possibility of 
refractory substances generated by fire being impressed by the 
forms of more fusible ones. It seems, however, that the same 
order of arrangement would prevail in substances that were 
suspended in a fluid medium, as the degrees of attraction would 
be the same. In either case, the first step by which the arrange- 
ment of an apparently homogeneous mass commenced, would 
probably be the accumulation of particular molecules into little 
globules. Such seems to have happened in variolites, and other 
rocks which contain spherical concretions of a different nature 
from their basis. Still farther advanced is the arrangement of 
porphyries : the molecules of one species have assumed a regular 
crystalline form ; and sometimes two or even more varieties of 
crystals are formed, which remain unmixed in the unarranged 
basis. If the remaining molecules of that basis are susceptible 
of crystallization, it may be fairly concluded, that an extension 
of the process of arrangement would convert the porphyry into 
granite, or at least into one of the compound aggregates of 
crystals which constitute the numerous tribes of granites, griin- 
steins, and sienites; and it seems equally probable that this 
might be accomplished, whether the molecules were indebted 
to a suitable temperature, or to an aqueous medium, for the 
requisite facility of movement 
The formation of granite and other rocks, must however be 
referred to the ultimate perfection of crystallization, by which 
