1890.] on Problems in the Physics of an Electric Lamp. 



41 



tbe bulb. We find the " Edison effect " is entirely absent, and that 

 the galvanometer current is zero. We have, as it were, placed our 

 target at such a distance that the longest range molecular bullets 



Fig. 8. 



6 



Collecting plate placed at end of a tube, 1 8 in. in length, opening out of the bulb. 



cannot hit it, or, at least, but very very few of them do so. Here 

 again is a lamp in which the plate is placed at the extremity of a 

 tube opening out of the bulb, but bent at right angles (Fig. 9). We 



Fig. 9 



ly 



Collecting plate placed at end of an elbow tube opening out of the bulb. 



find in this case, as first discovered by Mr. Preece, that there is no 

 "Edison effect." Our molecular marksman cannot shoot round a 

 corner. None of the negatively-charged molecules can reach the 

 plate, although that plate is placed at a distance not greater than 

 would suffice to produce the effect if the bend were straightened out. 

 Following out our hypothesis into its consequences would lead us to 



