II On the structure of magelona

The rest of the diagram represents the forces which we found when the disks were at distances of 10 and 5 millims. asunder. The forces which presented themselves at these distances are to be attributed mainly to a true Crookes’s reaction between the disks ; and they seem to warrant the conclusion that Crookes’s reaction was manifested at a dis­ tance of at least 10 millims. in a hydrogen vacuum, when the outstand­ ing tension was as much as 5 millims. of mercury. At distances of from 20 to 80 millims. the very feeble force acting on the glass disk in our apparatus seemed to vary about inversely as the tension. As already mentioned, it appeared to be nearly independent of the distance when the distance exceeded 20 millims. _ At distances of 5, 10, and 20 millims. the force on the swinging disk made some approach to varying at each tension inversely as the distance. But, so far as may be judged from our measures of such exceedingly feeble forces, there is a sensible deviation from this law at most of the