THE ELECTRIC CHARGES ON THE SPORES 193 



handle of the commutator was turned to the right so that the 

 plates were uncharged, the spores could be seen falling vertically 

 downwards between them at the rate of about 1 mm. per second. 

 No attraction of the spores to the plates could be detected. When 

 spores were observed to have reached the centre of the space between 

 the plates, the handle of the commutator was suddenly turned 

 to the left so that one of the plates became positively and the 

 other negatively charged. Immediately the paths of most of the 

 spores were altered (Fig. 68, A). Some spores were attracted to 

 one plate and some to the other, the majority going to the one 



Fig. 67. — Apparatus with electrical attachments for detecting the electrical 

 charges on falling spores. The brass chamber B, natural size. Description 

 in the text. 



with a positive charge. A few continued their motion vertically 

 downwards. A number of spores appeared to turn at right angles 

 to their former courses and they then moved with great rapidity 

 to the plates. These must have been the spores which were 

 relatively the most highly charged. Others made their way to 

 the plates at a more or less gentle angle to the vertical and with 

 a less accelerated velocity. Doubtless they were less highly 

 charged. A certain number of spores which were not appreciably 

 affected by charging the plates were probably not electrified at all. 



On reaching one of the plates, each spore became charged with 

 electricity of the same sign as that on the plate, and in consequence 



N 



