OF HIGH EEFE AN GIBILIT Y UPON GASEOUS MATTEE. 
3G1 
light scattered by this anterior cloud was very powerful. At the distant end of the tube 
the action was feeble. I reversed the tube ; but the precipitation here was by no means 
so prompt and copious as at the other end, into which the vapour had been evidently 
swept by the air and nitric acid. 
The lamp was suspended for about five minutes ; on reigniting it a coarse cloud was 
found within the tube ; but instantly through this coarseness a finer cloud of exquisite 
colour, luminousness, and texture was shed. A violent whirling motion was set up at the 
same time. The longitudinal lobes in this case were very curiously found. 
II. Air and iodide-of-isopropyl vapour . . . 8 inches; then 
Air and nitric acid . 8 inches. 
Tube optically empty, but in the fraction of a minute a shower of very coarse parti- 
cles had fallen upon the beam. They augmented up to a certain point and then ap- 
peared to diminish. The reversal of the tube caused fresh precipitation. The ren- 
dering of the beam more convergent also caused augmented precipitation, but nothing so 
fine as in the last experiment. The action, indeed, was altogether inferior to the last in 
point both of beauty and of energy. 
I suspended the lamp for a few minutes ; on restarting it the tube appeared empty, 
but in a moment a cloud much finer than that at first obtained was precipitated on 
the beam. Curious masses of particles gushed at irregular intervals upon the beam. 
On reversing the tube the action was decidedly finer than at first. 
Thus, suspending the lamp after it has been acting for a time, the vapour during 
the period of suspension undergoes a change which enables it to fall as a finer and more 
visibly copious cloud than at the beginning of the action. 
III. Air and nitric acid 1 inch ; then 
Air and iodide-of-isopropyl vapour . . . 15 inches. 
Action commenced immediately, and in less than a minute the beam had filled the 
tube with an unbroken cloud. The beam was rendered parallel, and the action con- 
tinued for eight minutes. The end nearest the light became rapidly empty, while in 
the distant half of the tube the particles fell in heavy showers. The whole tube subse- 
quently became almost empty ; the disappearance of the dense cloud first generated was 
very striking. It would appear as if after the first sudden precipitation evaporation 
had set in and restored the particles to the gaseous condition. 
Nitrite of Amyl (C 5 H n ONO) : — A transparent yellowish liquid. 
Contents of experimental tube. 
I. Air and nitrite-of-amyl vapour 1 inch ; then 
Air and nitric acid 15 inches. 
The tube was optically empty at starting ; action commenced in half a minute, the 
