DR. OLIVER LODGE 0'S ABERRATION PROBLEMS. 
759 
them out again. Also the bearings of the armature are, at present, hardly tight 
enough. Difficulties such as these have hitherto prevented the whirling machine 
from being quite satisfactory. At about 800 revolutions a minute a tremor begins. 
Fig. 9. 
Whirling machine for ether experiment, with pair of steel disks, I yard in diameter. From a photograph 
taken during preliminary tests, before it was bolted down to stone pier. Full voltage is always 
supplied to the field magnets, variable resistance is in armature circuit only. The brass tube 
conducts away surplus oil. Drawings of the machine are given in Plate 32. 
At high speeds it steadies itself, but at specific speeds the tremor re-occurs, and at 
some of the highest speeds is rather alarming. At others, however, the tee-totum 
action steadies the spin, and at these only could observations be made. 
