118 Scientific Intelligence. 
; mental purposes; yet it is absolutely impossible that the force can be 
rigorously uniform through the smallest finite bulk of the magnetic 
field in any such arrangement, or, generally, in any locality external 
toa magnet. If an experimenter wants a rigorously uniform fiel 
force, he can have it only in the interior of his magnet; and he must 
be contented not to see the action he experiments on at the time it 
portant fundamental properties of electrical force. It would be easy to 
make a hollow electro-magnet, in the interior of which the experimenter 
could observe with the minutest accuracy the bearings of all kinds and 
shapes of bodies in a rigorously uniform field of force. Ail that is ne- 
cessary to make such a conductor is to take a hollow papier-macheé 
globe, say six feet in diameter, and roll a galvanic wire over its surface 
in a succession of close parallel circles, -having their planes at equal 
distances from one another. hollow non-magnetic body o 
shape, cubical for instance, may have a rigorously uniform distribution 
without seeing them at the time they are taking place. Interesting 
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. imum or minimum points, can possibly give a uniform distribution of 
latenaity through ever so small a finite bulk of the field. 
ry Boas 
