PROCEEDINGS OF GEOLOGICAL SOCIETIES. 
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0 tinuation of the temperature speedily induced another change ; the texture 
e of the cooling material became more granular, its colour more grey, and 
the briUiant points larger and more numerous. These brilliant molecules 
1 arranged themselves in regular forms, and finally the whole mass became 
r pervaded with thin crystalline lamina3. Mr. Watt applied these facts in 
rj explanation of the globular structure which is observed in decomposing 
i basaltic rocks ; but as similar experiments have been often repeated, the 
s results are familiarly known to every geologist, and need not be further 
alluded to in this paper. Sir James Hall, in 1805, conducted experiments 
, illustrating the crystalline arrangements and texture assumed by basaltic 
rocks when fused and cooled under high pressure. He established the fact 
that most rocks of presumed iy,neous origin, when fused, yielded different 
products according to the differences in the amount of pressure under 
which they were cooled. Tiius, when the rate of cooling was rapid, they 
formed a black amorphous glass ; and when the cooling was slow, a strong 
mass with a granular structure. The same materials yielded the most 
dissimilar products, — a fact that is of the greatest importance in reference 
to the study of the nature of eruptive rocks, and of the metamorphic action 
which they occasion. These discoveries were chiefly valuable from their 
philosophical bearing upon contested points in the science of geology ; and 
it was not until the year 1816 that any attempt was made to turn them to 
a practical and economical value. At that tnne, acting U};o:i the resalts of 
some experiments which had been made upon the Continent, a Mr. Joan 
Michel Borgognon took out a patent in England for the manufacture of 
articles of utihty in what he termed artificial basaltic lavas. His inven- 
tion claimed the discovery of operating upon stony substances, but chiefly 
upon the vitreous slags from iron furnaces. These were fused at a high 
temperature, and run into moulds of cast-iron or refractory clay, the 
moulds being heated in the interior by means of a powerful flame, kept up 
by a blast. Colouring matter, from the oxides of iron and other metals, 
was mixed with the fused materials, and great diversity and beauty was 
thereby obtained in the vitreous ornaments. It does not appear, however, 
that any great application of his patented lavas was made in England. In 
the year 1851 Mr. Henry Adcock, a civil engineer, of Oldbury, took out 
the first patent for the production of bricks, tiles, pipes, etc., from the fused 
trap of liowley Ecgis. This gentleman had been led to the application of 
this material from experiments which he had commenced in the year 1831. 
He then fused some Kowley liag in a common kitchen-fire ; and beinjj; much 
impressed with the beauty of the black glass as it fell on the hearth, he 
perceived that it might probably possess great practical value. He ob- 
tained the use of a reverberating furnace, and conducted his experiments 
upon a larger scale. In 1851 a patent was obtained, in which the inventor 
claimed for his discovery the melting the stony material known as Basaltic 
Trap, Eowley Eag, or Whinstone, and running the same when in a fluid 
state into moulds. The materials were heated in a reverberating furnace, 
either at the bottom or in crucibles, and then cast into cast-iron moulds 
put together with iron cramps. The fused trap was rfm into the moulds, 
when both were brought into a state of white heat. If it were intended 
to give a polished surface to the casting, the cast-iron mould was highly 
polished and coated with plumbago, also highly polished. If the fused 
materials were allowed to cool at a gradual and slow rate of cooling, the 
result was a hard stony rock, scarcely to be distinguished from the original 
trap from Eowley Eegis ; but a less degree of heat, with a quicker rate of 
cooling, caused the materials to assume the appearance of a mixed marble ; 
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