260 Scientific Intelligence. 
was a circle, thinnest at the center, and_augmenting uniformly in 
thickness from the center outward. hen placed in its proper 
position between the Nicol and the cloud, it cahibited a system of 
splendidly colored rings. 
The cloud pee gate to — the first operated upon in the 
manner pineal ‘ may, however, be greatly improved upon 
by the choice of ae bathiasioes, aan by the application in prop- 
or mixed with air in the experimental tube, Seti ir the action of 
light, or shows but a feeble result of this action, Baad ye placing 
it in Fight vig with another gas or vapor, be caused to exhibit 
Dry air was permitted to bubble through the liquid nitrite of 
butyl! until the experimental tube, which had been previously ex- 
hausted, was filled with the mixed air and vapor. The visible 
ydrochloric acid. On the beam through this mixture, 
the action paused any sufficiently long to show that at the mo 
ment of commencement tube was optically empty. But the 
? t 
am amounted only to a een fraction of a second, a dense cloud 
ene an imm epee precipitated upon the beam which traversed 
the 
This Boal began blue, but the advance to whiteness was so rapid 
as almost to justify the application of the term instantaneous 
The dense semis looked at perpendicularly to its axis, showed 
ion was Pesos 
mks experimental tube being again cleansed and exhausted, Bo 
mixed air — nitrite-of-butyl vapor was org to tye it unt 
ited mi 
whe Of re. ir pa a solut 28 
of hydrochloric acid was then added till the mercury | oa we 
depressed three inches. The condensed beam of the electric light 
assed for some time i thie through this mixture. There wa® 
absolutely nothing within the tube competent to scatter the light 
n, however, a superbly blue cloud was formed along the ae 
e. the beam, and it continued blue sufficiently long to perm! 
thorough examination, The light discharged from the cloud at 
* 
