[ G« ] 
XVI. Contributions to Molecular Physics in High Vacua. 
Magnetic Deflection of Molecular Trajectory.—Lairs of Magnetic Rotation in High 
and Low Vacua.—Phosphorogenic Properties of Molecular Discharge. 
By William Crookes. F.R.S. 
Received March 27,—Read April 3, 1879. 
Contents. 
Par. 
Non-phosphorescence in dark space round 
negative pole. 587 
Direction of molecular rajs nearly normal to 
pole. 590 
Phosphorescence deadened by repeated excite¬ 
ment . 592 
Shifting of line of molecular discharge .... 595 
Experiments with idle pole and screen. 597 
Positive potential of idle pole. 601 
Penumbra of uninsulated screen . 602 
Theory of umbra and penumbra . 604 
Experiments with a swinging idle pole. 606 
Lateral repulsion of parallel rays of molecular 
discharge . 609 
Par. 
Magnetic deflection of molecular trajectory. . 611 
Action of the earth’s magnetism . 617 
Continuous rotation of molecular discharge.. 618 
Law of magnetic rotation in high and low 
vacua. 619 
Pkospkorogenic properties of molecular dis¬ 
charge . 629 
Phosphorescence of luminous sulphides, dia¬ 
monds, and natural and artificial rubies . . 630 
The alumina line in the spectrum. 633 
Professor Maskelyne on the connexion be¬ 
tween molecular phosphorescence and crys¬ 
talline structure . 634 
586. The present paper is a continuation of the Bakerian Lecture “On the Illumina¬ 
tion of Lines of Molecular Pressure and the Trajectory of Molecules,” read before the 
Royal Society, December 5, 1878. Phenomena there briefly referred to have since been 
more fully examined ; new facts have been observed, and their theoretical bearings 
discussed ; and numerous experiments suggested by Professor Stokes and others have 
been tried, with the result of acquiring much information which cannot fail to be of 
value in assisting to evolve a theory capable of embracing all the phenomena under 
discussion. 
587. In par. 514 1 described a piece of apparatus by means of which the molecular 
rays electrically projected from the negative pole at a high exhaustion were converged 
to a focus, the pole itself being hemi-cylindrical in shape. On referring to the coloured 
drawing illustrating the experiments it will be observed that the green phospho¬ 
rescence of the glass (by means of which the presence of the molecular rays is mani¬ 
fested) does not take place close to the negative pole. It has been since found that 
4 N 2 
