578 FRAGMENTS OF SCIENCK. 
as to prompt the conclusion that the apparently pure flame of the 
alcohol -lamp required but a beam of sufficient intensity to reveal its 
clouds of liberated carbon. 
But is the blackness smoke? This question presented itself in a 
moment, and was thus answered: A red-hot poker was placed under- 
neath the beam; from it the black wreaths also ascended. A large 
hydrogen flame, which emits no smoke, was next employed, and it 
also produced with augmented copiousness those whirling masses of 
darkness. Smoke being out of the question, what is the blackness? 
It is simply that of stellar space; that is to say, blackness resulting 
from the absence from the track of the beam of all matter competent 
to scatter its light. When the flame was placed below the beam, the 
floating matter was destroyed in situ,' and the heated air, freed from 
this matter, rose into the beam, jostled aside the illuminated particjes, 
and substituted for their light the darkness due to its own perfect 
transparency. Nothing could more forcibly illustrate the invisibility 
of the agent which renders all things visible. The beam crossed, un- 
seen, the black chasm formed by the transparent air, while, at both 
sides of the gap, the thick-strewn particles shone out like a luminous 
solid under the powerful illumination. 
Supposing an infusion intrinsically barren, but readily 
susceptible of putrefaction when exposed to common air, to 
be brought into contact with this unillurninable air, what 
would be the result? It would never putrefy. It might, 
however, be urged that the air is spoiled by its violent cal- 
cination. Oxygen passed through a spirit lamp flame is, 
it may be thought, no longer the oxygen suitable for the 
development and maintenance of life. We have an easy 
escape from this difficulty, which is based, however, upon 
the unproved assumption that the air has been affected by 
the flame. Let a condensed beam be sent through a large 
flask or bolthead containing common air. The track of the 
beam is seen within the flask the dust revealing the light, 
and the light revealing the dust. Cork the flask, stuff its 
neck with cotton-wool, or simply turn it mouth downward 
and leave it undisturbed for a day or two. Examined 
afterward with the luminous beam, no track is visible; the 
light passes through the flask as though a vacuum. The 
floating matter has abolished itself, being now attached to 
the interior surface of the flask. Were it our object, as it 
will be subsequently, to effectually detain the dirt, we might 
coat that surface with some sticky substance. Here, then, 
without " torturing" the air in any way, we have found 
a means of ridding it, or rather of enabling it to rid itself, 
of floating matter. 
