PROCEEDINGS OF SOCIETIES. 303 
bonaceous particles.* When this dust is examined under the 
microscope with a power of forty or fifty diameters, it is found 
to consist of ferruginous matter and crystallised substances, some 
particles transparent, others white and red. It contains also a 
number of curious-looking objects, which vary considerably in 
size and colour. The majority of these bodies are spherical, and 
when separated from the irregularly shaped particles forming the 
bulk of the dust they become interesting objects for the micro- 
scope. I shall confine my remarks more especially to these 
globular bodies. Some of these are as perfect in form as the most 
carefully turned billiard balls, and have a brilliant polish. The 
various colours which these globules exhibit give additional interest 
to theirexamination. Some are transparent crystal spheres, others 
are opaque white, many are yellow and brown, and variegated 
like polished agates or carnelian of different shades. The most 
abundant of the highly polished balls are black ; there are others 
which look like rusty cannon balls—some of these have an aper- 
ture in them like a bomb shell, and many are perforated in all 
directions. To obtain these objects the dust should be washed 
in a bowl and all the lightest particles allowed to float away; the 
remainder consists of fragmentary crystalline and ferruginous 
substances ; mixed with these are the polished balls described, 
which, under the microscope, by a brilliant reflected light, look 
like little gems. To separate the spherical bodies from the irre- 
gular ones it is only necessary to sprinkle some of this material 
on an inclined glass plate, and by gentle vibration the balls roll 
down, and can thus be collected. Having satisfied ourselves with 
the examination under the microscope, it is natural that we 
should desire to know more about these novel objects. What is 
their elementary constitution ? Why are they spherical ? Howdo 
they get into the flue? I have not attempted a chemical analysis 
of these minute bodies, many of which are less than the 100th part 
of an inch in diameter. I can only therefore offer an opinion as to 
their probable constitution, judging from what is known of the 
chemical analysis of coal ash, and from the appearance they present 
under the microscope. Referring to the chemical analysis of coal 
ash, we find that it sometimes contains silica, magnesia, alumina, 
sesqui-oxide of iron, lime, soda, potash, sulphate of calcium, 
anhydrous sulphuric acid, anhydrous phosphoric acid, sulphur, and 
sometimes traces of copper and lead. The vegetable origin of 
coal is now generally admitted, and doubtless some of the sub- 
stances I have just named have been taken up by the coal plants, 
whilst other portions may have collected in the locality where 
the coal was formed. As this is not immediately connected with 
our present inquiry, I proceed to speculate as to the constitution 
of these globular bodies. The transparent spheres I imagine to 
be silicates of soda or potash ; the opaque white are most likely 
silicate of soda of potash combined with lime and alumina; the 
yellow and brown are silicates coloured by iron in different pro- 
* My attention was drawn to this subject by Mr. Johnson, of Wigan, in 
November, 1860. 
