CHEMISTRY. 179 



ter of curious-looking objects, which vary considerably in size and 

 color: the majority of these bodies are spherical, and, when sepa- 

 rated from the irregularly shaped particles forming the bulk of 

 the dust, they become interesting objects for the microscope. 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 colors 

 which these globules exhibit give additional interest to their ex- 

 amination. Some are transparent crystal spheres, others are 

 opaque white, many are yellow and brown, and variegated like 

 polished agates or cornelian of different shades. The most abun- 

 dant of the highly polished balls are black ; there are others which 

 look like rusty cannon-balls ; some of these have an aperture in 

 them like a bomb-shell, and many are perforated in all directions. 

 To obtain these objects, the dust must be washed in a bowl, and 

 all the lightest particles allowed to float away; the remainder 

 consist 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 irregular 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 ? How do 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 constitu- 

 tion, 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, sesquioxide of iron, 

 lime, soda, potash, sulphate of lime, anhydrous sulphuric acid, 

 anhydrous phosphoric acid, sulphur, and sometimes traces of cop- 

 per and lead. The vegetable origin of coal is now generally ad- 

 mitted, and, doubtless, some of the substances I have just named 

 have been taken up by the coal plants, while 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 silicates of soda or potash com- 

 bined with lime and alumina ; the yellow and brown are silicates 

 colored by iron in different proportions. The black globes are not 

 all alike in composition ; some of these are silicates colored by 

 carbon, others are iron balls coated externally with a silicate. 

 Many of these rusty cannon-balls are probably ferrous oxide 

 formed by the action of heat on the iron pyrites in the coal. 

 There are also balls of black magnetic oxide ; the perforated shells 

 are probably ferrous sulphides. The globular form of these 

 bodies suggests that they have been thrown off in scintillations, 



