286 
Mr . Watt’s Observations 
It seems obvious, that an equalized temperature would have 
rendered the whole similar to the substance last described ; and 
it may be fairly inferred, that by a continuance of heat, the 
minute crystals would have been augmented in their dimensions, 
by the accession of molecules still engaged in the basis, or by 
the union of several crystals, till they acquired sufficient mag- 
nitude for their nature to be absolutely determined by the usual 
modes of investigation. It is probable, however, if such pre- 
cautions had been taken as might have secured this degree of 
perfection in the ulterior result, that the mass would only have 
exhibited an uniform aspect, and that the interesting initial phe- 
nomena would not have been discovered.* 
There are some considerations which appear to offer a partial 
explanation of the formation of the globules, and of the radiated 
spheroids. It is well ascertained that heat is emitted by all 
bodies, in their change from a gaseous to a fluid state, and also 
These minute points are soon obliterated by the large curves of the fibrous spheroids, 
which give a mamellated form to the interiors of the cavities; and, when the crystals 
are generated in the mass, they shoot into some of the cavities, and line them with 
their brilliant laminae. 
* In this and the succeeding paragraphs, the word molecule is used in the sense 
assigned to it by Hauy and Dolomieu, and is understood to represent the peculiar 
solids, of definite composition and invariable form, the accumulation of which, forms 
the crystals of mineral substances. Such molecules, preserving their form and their 
essential characteristics, may be extracted from most crystals by mechanical division, 
and may be subdivided as far as our senses can recognise them. Though we cannot 
by mechanical means directly divide them into their elementary particles, we are 
enabled to effect this by chemical solution, the only power to which their aggregation 
yields. It will be evident, from the observations that follow, that I am inclined to 
adopt the ingenious idea of Dolomieu, that many apparently homogeneous rocks are 
compounds of the minute molecules of several species of minerals ; and that, where a 
suitable opportunity is given, these will develope themselves by the formation of their 
peculiar crystals. 
