144. On the Law of Action between Magnets. 
Values were calculated for P’ from the observations at 22'5 
and 30 cms., and from those at 30 and 40 ems. The mean 
results appear in Table XXII. 
TaBLeE XXII, 
| Observed P'-—f(a, 5). : P(A, X’) allowing for Q and R, 
Magnet | 1 0 cl ra 
(deflected. (a, 6). 4 | _ | 
22°55 & 80 | 80&40 | 225&30| 30440 | ya 
| | ems.) | . ems, |. emis. ems. | ii? 
iG CaM aur: ETT | van 
AM sccee.| *0 323 | 192 | —0383 | —031 | —082 
Na ...... 08 Bay Ve pote, E023 —0-90 | —0'33 
MO een ‘03 CSA He ES OP) we 8-94 —317 | —3:55 
In allowing for Q and R, p was taken as °81, and the ob- 
servations were not numerous, so that high accuracy cannot 
be claimed ; but the difference between Ne and the two other 
magnets is conspicuous. Again, taking the mean observed 
values obtained above for P(A,2’), and employing 2A to 
denote the pole-distance of the magnet KC1, we have 
2.7 — 3A" = — ‘oe 
20.7 —3A."= — °33 > whence 
aN? — oh = — 
The agreement with the values 1:19 and 1:07 obtained for 
As?—A,” and A,?—A,” in Table XIX. is very satisfactory. 
§31. During the deflexion experiments the magnetic 
moments of the magnets, in C.G.S. units, were approximately 
as follows : 
AN. Na. Ne, 60 138 140 
250 310 217 333 285 222 
Ae —A’= 1:08 
rg” —Ay? = L008 
Of the Jones magnets Ne thus possessed the lowest 
moment as well as the greatest pole-distance ; but amongst 
the other three magnets 140 had both the lowest moment and 
the smallest pole-distance. Also the difference between the 
moments of Ne and AN is less than the difference between 
AN and Na, which seemed practically identical so far as 
pole-distance is concerned. The facts thus throw no certain 
light on the question whether the strength influences the pole- 
distance. 
The Jones magnets, as already stated, are very old. They 
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