NEW CHEMICAL REACTIONS. 91 
neutral point to the observer's eye measured in the first 
instance 66 degrees. 
The windows of the laboratory were now opened for 
some minutes, a portion of the incense-smoke being per- 
mitted to escape. On again darkening the room and turn- 
ing on the light, the line of vision to the neutral point was 
found to enclose, with the axis of the beam, an angle of 63 
degrees. 
The windows were again opened for a few minutes, more 
of the smoke being permitted to escape. Measured as be- 
fore, the angle referred to was found to be 54 degrees. 
This process was repeated three additional times; the 
neutral point was found to recede lower and lower down 
the beam, the angle between a line drawn from the eye to 
the neutral point and the axis of the beam falling succes- 
sively from 54 degrees to 49 degreees, 43 degrees and 33 
degrees. 
The distances,roughly measured, of the neutral point from 
the lamp, corresponding to the foregoing series of observa- 
tions, were these: 
1st observation 
2d 
3d 
4th 
5th 
6th 
2 feet 2 inches. 
At the end of this series of experiments the direction of 
maximum polarization had again become normal to the 
beam. 
The laboratory was next filled with the fumes of gun- 
powder. In five successive experiments, corresponding to 
five different densities of the gunpowder-smoke, the angles 
enclosed between the line of vision to the neutral point and 
the axis of the beam, were 63 degrees, 50 degrees, 47 de- 
grees, 42 degrees, and 38 degrees respectively. 
After the clouds of gunpowder had cleared away, the 
laboratory was filled with the fumes of common resin, ren- 
dered so dense as to be very irritating to the lungs. The 
direction of maximum polarization enclosed, in this case, 
an angle of 12 degrees, or thereabouts, with the axis of the 
beam. Looked at, as in the former instances, from a 
