48 
MR. S. W. J. SMITH ON THE THERMOMAGNETIC ANALYSIS OF 
5 
4 
3 
A 
2 
I 
meteorite. The observation k showed that the permeability, after slow cooling from 
a temperature beyond the critical point, was nearly the same as that first observed. 
The observations l and m were next made in order to get values of p near the 
temperature of maximum permeability. 
After the experiments just described, no further measurements were taken until 
the isolated observation represented by n was made with the object of filling a gap, 
at about 550° C., in the previous observations. After being allowed to cool from the 
temperature just stated, the ring was left for about three months without further 
observation. The experiments represented by the numbers 1 to 63 were then begun. 
I was surprised to find that the permeability at ordinary temperature was about 
30 per cent, higher than the value ( Jc ) last observed at that temperature, and it 
seemed as if the permeability had risen in that proportion in the three months during 
which the ring; had been left undisturbed. It seemed advisable to examine whether 
this apparent time effect, so pronounced at ordinary temperature, was accompanied 
by any change in the variation of p at higher temperatures. The experiments 2, 3, 
and 4, 5 showed an apparently anomalous position, with respect to one another, of 
the points 3 and 4. For this reason - the observations at these temperatures were 
repeated (see 7. and 8), as. was that at the higher temperature (see 9). It was found 
.that although the permeability at ordinary temperature seemed to change appreciably, 
Fig. 9. Meteoric iron (1st winding). 
Relation between permeability (H = 0 - 48 C.G.S. approximate) and thermal treatment. 
C.G.S. values of p = ordinates x 135‘5 (approximate). 
