12 Arthur Aikin, Esq. on a series of 
From the above described specimens, we may conclude that glass 
when exposed to a long continued natural heat, undergoes changes 
of structure very analogous to those which have been produced on 
this substance in our laboratories, by burying it in red hot sand, 
except that (as might be expected) the slower process has produced 
the more crystalline structure. The slight change of structure 
produced in those specimens, which have actually undergone fusion, 
also coincides in a remarkable manner with the experiments of 
Reaumur, who first directed the public attention to this interesting 
subject, which has since been applied, very ingeniously and plausibly 
at least, to the solution of a very important class of geological 
phenomena. 
The changes produced on bars and utensils of iron, are not less 
remarkable than those which have already been described, and since 
they have not been anticipated by analogous experiments, made pur- 
posely in the laboratory, I shall take the liberty of mentioning them 
somewhat in detail. 
No. 12 is a mass of iron, probably a piece of a cylindrical bar. 
The external part of the specimen, although rifted longitudinally, 
exhibits a considerably compact structure, and appears to be a mix- 
ture of the black and red oxides of iron ; it dissolves without 
effervescence in muriatic acid, and acts on the magnetic needle, but 
not very powerfully. The interior is a mass of grey oxide in 
confusedly octohedral crystals, acting very strongly on the magnetic 
needle, but not possessed of polarity. 
Nos. 13 and 14 differ but very little from No. 12, except that 
some of the cells are lined with a white vitreous substance, from 
which acicular crystals of the same have shot from one side of the 
eell to the other. 
No. 16 is part of a tube which has been reduced to the state of 
