354 



THE GEOLOGIST. 



and a rapid rate of cooling produced a black glassy substance, quite opaque, 

 unless it was cast very thin, and then it became semi-transparent. If it 

 •were desired to run the fused materials more quickly, a flux, such as soda, 

 effected such a result. The practical utility of this invention became widely 

 known, and an extensive application of it was made in ornaments of an 

 architectural character, mantelpieces, window-sills, window-heads, string 

 courses, capitals of columns, and monumental slabs, which were all cast 

 from Rowley Rag ; and these, from the almost imperishable nature of the 

 material, are likely to endure for ages. For reasons which it is not neces- 

 sary to state, the works did not long continue, and have since been taken 

 down. In 1852 Mr. W. G. Elliott, Blisworth, took out a patent for the 

 manufacture of pipes and other articles from mixed brick clay, limestone, 

 ironstone, and oyster-shells. The product was a greenish-black vitreous 

 material when run into press-moulds and afterwards annealed. There is 

 very little difference between this application and that of Mr. Borgognon, 

 and it added nothing which was not well known in the effects of heat upon 

 minerals. In 1854 a patent was taken by Mr. J. T. Chance, of Birmingham, 

 claiming improvements in the manufacture of articles from the mineral 

 called Rowley Rag, in which the principal discovery, in addition to what 

 had been known of its fusibility and of its adaptation for casting in moulds, 

 was, that the fused mineral, unlike cast-iron, was capable of being rolled 

 or pressed into the form of slabs, sheets, bars, and rods, all either with 

 plain or raised ornamental surfaces. In fact, it could be treated in the 

 same manner as plate-glass and some of the ductile metals ; but articles 

 manufactured in this way required to be subjected to the process of 

 annealing. Another discovery was made about this time, in which it was 

 shown that it was possible to mix a quantity of coloured glass with the 

 fused Rowley Rag, for the specific gravity of basalt and common glass, 

 when in a state of fusion, are nearly alike, and advantage was taken of this 

 to produce sheets of the material which, when polished, resemble the rich 

 and beautifully-coloured serpentines of Cornwall. In fact, there was no 

 limit to the variety which could have been obtained by the admixture of 

 these two and other substances, — the only point of any scientific interest 

 in the matter being that the two materials did rot chemically combine, even 

 with the greatest amount of care and skill. They were only mechanically 

 mixed together, and the result is well shown in the specimens upon the 

 table. In 1855 Mr. Chance and Mr. Adcock took out a further patent for 

 improvements in casting articles from the slags of iron furnaces, but this 

 chiefly related to the machinery and method of casting in sand moulds in 

 place of the iron moulds first used by Mr. Borgognon ; and since this 

 date no further discoveries appear to have been made in the practical appli- 

 cation of the basalts and traps for economic purposes, or in the aid of the 

 decorative arts. 



The specimens exhibited by the author, in illustration of his paper, were 

 obtained from Mr. Adcock, the inventor and proprietor of the Basaltic 

 Stone Works, at Olclbury, Worcestershire, after the works were discon- 

 tinued ; namely, Rowley Rag in its natural state ; a shining opaque 

 glass — artificial obsidian — the common result of the Rowley Rag when 

 cooled very qui ckly ; specimen showing the conchoidal fracture, which is 

 common to the fused as well as to the natural state of the Rowley Rag ; 

 specimens showing different amounts of recrystallization in accordance 

 with the rates of cooling (in one the greatest degree of change ever ob- 

 tained was shown, other than its entire conversion into basaltic stone) ; a 

 specimen showing that in some instances the recrystallization takes place 



