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ARRANGEMENT IN FIRST EXPERIMENTS 17

it and in this hole a tube F with a very fine bore was irmly
fixed ; it is essential to the success of the experiment that the.
bore of the tube should be exceedingly fine so as to get a small,
well-defined patch when the positive rays strike the screen, S.
This was a flat glass plate uniformly covered with powdered
willemite which phosphoresces much more brightly than glass
when struck by the rays. M and N are the poles of the electro-
magnet, and P! P₂ the parallel metal plates used to produce
the magnetic and electric fields respectively; //, W,W are

FIG. 7. FIG. 8.

sheets of soft iron to screen the discharge taken from the
magnetic field due to the electromagnet

The effect observed on the screen depends to a very great
extent upon* the pressure of the gas in the tube; when this was
not exceedingly low, the phosphorescence under the action of
the magnetic and electric fields was drawn out into two con-
tinuous straight bands as in Fig. 7. The value of ejm for the
most deflected portion of the band a, was io⁴, for that of band
6₉ 5 x io⁸. These correspond to the values of ejm for the atom
and molecule of hydrogen respectively, suggesting that the
one band is due to hydrogen atoms, the other to hydrogen



	ARRANGEMENT IN FIRST EXPERIMENTS 17 it and in this hole a tube F with a very fine bore was irmly fixed ; it is essential to the success of the experiment that the. bore of the tube should be exceedingly fine so as to get a small, well-defined patch when the positive rays strike the screen, S. This was a flat glass plate uniformly covered with powdered willemite which phosphoresces much more brightly than glass when struck by the rays. M and N are the poles of the electro- magnet, and P! P₂ the parallel metal plates used to produce the magnetic and electric fields respectively; //, W,W are

	FIG. 7. FIG. 8. sheets of soft iron to screen the discharge taken from the magnetic field due to the electromagnet The effect observed on the screen depends to a very great extent upon* the pressure of the gas in the tube; when this was not exceedingly low, the phosphorescence under the action of the magnetic and electric fields was drawn out into two con- tinuous straight bands as in Fig. 7. The value of ejm for the most deflected portion of the band a, was io⁴, for that of band 6₉ 5 x io⁸. These correspond to the values of ejm for the atom and molecule of hydrogen respectively, suggesting that the one band is due to hydrogen atoms, the other to hydrogen