94 A Microscopie Examination — [Moura Aue tee 
reddish, or white and opaque. Some transparent pieces with a 
glassy fracture were noticed, and were regarded as glass resulting 
from the fusion of sand used in the welding process. An extremely 
fine powder—the dust of the dust—was sedulously examined for 
germs or spores, but it presented angular shapes and colours iden- 
tical with the other matters. The particles varied in size, say, from 
soyooth to soceooth of an inch. A most interesting object was 
the iron, which was present in the form of balls. These were 
found to be hollow, and the fragments of their shells were discovered 
to be translucid: a granular structure was noticed in them. These 
iron bombs or balloons varied from 345th of an inch to spyoth, 
having been measured with the micrometer. The diameter of a 
bomb of zj5oth of an inch was computed to be sixteen times greater 
than the thickness of the shell, which would therefore be about the 
sobooth of an inch. This computation was made in order to find 
at what degree of thinness its iron-material was translucent. [The 
iron was supposed to be present as magnetic oxide.| There were 
no spores nor seeds present, no fibres of any kind the result of 
developing germ-life—no fibres at all, except a few cotton filaments 
from the garments of artisans, fibrous carbon particles, and a speci- 
men of contorted branchy metal. There were no germs here, yet 
the sunbeams were full of dancing motes, whose portraits were shown 
on the diagram. The ray, shining on them, assumed, in conse- 
quence of their hue, a bluish colour, similar to that observed when 
the carboniferous smoke of a candle or lamp is placed in the track 
of a sunbeam. On entering such an atmosphere, the taste of 
carbon, and indeed of iron, may be readily perceived. The dust 
might serve as a cheap stomachic for those who use charcoal biscuits 
or charcoal and bismuth powder. 
Although a great quantity of this iron, carbon, and ash must 
daily pass in and out of the lungs; and besides, although a certain 
percentage must remain in them (as shown by Pouchet’s dissections 
and Professor Tyndall’s experiments), it was difficult to find a 
healthier body of men than those who work in such factories. One 
young man, whose lungs were weak, suffered from hemoptysis 
(blood-spitting, with cough), which he had contracted m an American 
foundry where the heat was excessive. He was observed in an atmo- 
sphere murky with these motes, and was asked did it not affect him 
injuriously ? He said, No; he found himself well in it; his cough 
came on at home on rising and lying down. ‘These facts seem to 
indicate that the carbon poured into the air of cities, from gas-lghts 
as from fires, may not have so injurious an effect as sometimes 
fancied, and may even tend to counteract the deleterious effects of 
some of the mucous particles. The prevention of black-smoke, 
whilst the injurious gases remained, might thus not be so exceeding 
great a service to the public health as popularly considered, although, 
