112 GERMINATION 



Experiment No. 6 : Laurel Leaf. 

 D = (in air) 170 mm. 



After one minute earthed in vacuo 

 D = (in vacuo) Zero. 

 Experiment No. 7 : Laurel Leaf. 

 D == (in air) 170 mm. +. 



After eight minutes earthed in vacuo 

 D = (in vacuo) Zero. In three minutes went to 

 40 mm. negative. 

 Experiment No. 8 : Hydrangea Leaf. 

 D = (in air) 165 mm. 



After twenty minutes earthed in vacuo 

 D = (in vacuo) Zero. 

 Experiment No. 9 : Hydrangea Leaf. 

 D =■ (in air) 132 mm. 



After fifteen minutes earthed in vacuo 

 D =■ (in vacuo) Zero. 

 Experiment No. 10 : Onion. R Needle to root ; L 

 Needle to foliage end. 

 D =• (in air) 2750 mm. negative (Full deflection, 

 500 ohm shunt). 



After twenty-five minutes earthed in vacuo 

 D =■ (in vacuo) Zero. 

 Upon the face of them these experiments appeared to be 

 quite conclusive and to prove, beyond any manner of doubt, 

 that all the deflections were due to air-charge. But it was 

 necessary to guard against the possibility of error, and 

 error might be introduced by 



1. Polarisation. 



2. The Nature of the Contacts altering, and 



3. Diffusion, with consequent neutrahsation of charge. 

 There was also the question whether earthing in vacuo 



produced a different effect from earthing in air. To deter- 

 mine these points further experiments were carried out, 

 with the following result : — 



1. Polarisation of electrodes did not play any appre- 

 ciable part in the phenomena, but 



2. Differences of Contact did, probably owing to one 



