PROFESSOR TYNDALL ON THE DIAMAGNETIC FORCE, ETC. 
17 
Table III. 
Bar of soft iron, No. 1. 
length 0'8 of an inch, 
width 0‘13 of an inch, 
depth 0*15 of an inch. 
Strength of current. 
168 
Attraction. 
168® 
214 
204® 
248 
253® 
274 
275 ® 
323 
313® 
362 
347" 
385 
374 ® 
411 
385® 
Table IV. 
Bar of bismuth. No. 1 . 
length 0*8 of an inch, 
width 0-13 of an inch, 
depth 0*15 of an inch. 
Strength of current. 
Repulsion. 
78 
78® 
136 
135® 
184 
191® 
226 
226® 
259 
259® 
287 
291® 
341 
322® 
377 
359® 
411 
386® 
These experiments prove, that, up to a strength of about 280, the attractive force 
operating upon the iron, and the repulsive force acting upon the bismuth, are each 
accurately proportional to the square of the strength of the magnetising current. 
For higher powers, both attraction and repulsion increase in a smaller ratio ; but it is 
here sufficient to show that the diamagnetic repulsion follows precisely the same law as 
the magnetic attraction. So accurately indeed is this parallelism observed, that while 
the forces at the top of the tables produce attractions and repulsions exactly equal to 
the square of the strength of the current, the same strength of 411, at the bottom of 
both tables, produces in iron an attraction of 385®, and in bismuth a repulsion of 
386®. The numbers which indicate the strength of current in the first column are the 
MDCCCLV. 
D 
