146 
matter than can he accounted for by the analysis of coal 
ash. I think the surplus may be regarded as representing 
the wear and tear of the iron work about the furnace, such 
as fire bars, boiler plates, &c. The brick work and cement 
about the boiler and flues may also supply some of the 
silica, alumina, and iron for these balls, numbers of which 
are merely thin shells. The movements of these objects, 
caused by the approach of a magnet under the stage of the 
microscope, are somewhat amusing, and it is at times 
startling to see the crystalline objects, both spherical and 
irregular, exhibit magnetic attraction : probably they con- 
tain particles of iron imbedded in them ; if they do not, 
may we not imagine that there is some magnetic compound 
in which the crystalline matter predominates ? When we 
consider the accidental condition under which this matter 
has combined, it is just possible that some new molecular 
arrangement or combination of elements may have taken 
place. It is very probable that many of these polished 
balls are much more complex in their elementary constitu- 
tion than I have stated. They are in fact a kind of glass, 
and many of them merely bulbs, Pelouze states that glass 
is probably an indefinite mixture of definite silicates. Glass, 
containing small quantities of ferrous oxides and sodic 
sulphates, when exposed to sunlight becomes yellow, and 
possibly some of these balls may have changed in colour 
since they came from the flue. Hydrochloric and nitric 
acid exert very little action on the ferruginous globes : this 
may be due in some measure to the high temperature at 
which the oxides have been formed ; in other cases they are 
no doubt protected by an external coating of some silicate. 
It would require much time and patience to collect a 
sufficient number of each kind of these minute objects for a 
chemical analysis; but the spectroscope might probably 
assist in revealing their constitution. When time permits 
I hope to resume the subject. 
