206 
thirds power showed a large proportion of fragments of iron, 
and on applying a soft iron needle I found that many of 
them were highly magnetic. They were mostly long, thin, 
and straight, the largest being about xi o of an inch, and, 
under the power used, had the appearance of a quantity 
of old nails. I then with a magnet separated the iron from 
the other particles. 
The weight altogether of the dust collected was 57 grains, 
and the proportion of those particles composed wholly or in 
part of iron was 2-9 grains, or more than one half. The 
iron thus separated consisted chiefly of fused particles of 
dross or burned iron, like “ clinkers,” many were more or 
less spherical, like those brought to our notice by Mr. 
Dancer from the flue of a furnace, but none so smooth ; they 
were all more or less covered with spikes and excrescences, 
some having long tails like the old “Prince Kupert’s drops”; 
there were also many small angular particles like cast iron, 
having crystalline structure. 
The other portion of the dust consisted largely of cinders, 
some very bright angular fragments of glass or quartz, a 
few bits of yellow metal, opaque white and spherical bodies, 
like those described by Mr. Dancer, grains of sand, a few 
bits of coal, &c. 
Af ter the examination of this dust, I could easily under- 
stand why it had produced such irritation ; the number of 
angular, pointed, and spiked pieces of iron, and the scoriae 
or clinkers, being quite sufficient to account for the un- 
pleasant effect. 
I think it probable that the magnetic strips of iron are 
laminae from the rails and tires of the wheels, and the other 
iron particles portions of fused metal, either from the coal 
or from the furnace bars. The large proportion of iron 
found in the dust is probably owing to the metal being 
heavier than the ordinary dust, and accumulating in cuttings 
such as those between the two stations named. 
