1309 
H, as well as on H,. Now it is true that we have also considered 
a somewhat “idealised” state, where no mutual action between the 
elementary crystals would exist and where all the “tipped over” 
magnetic moments would keep their direction, as long as the exter- 
nal field did not place them in the opposite direction, and which 
therefore might be called a state of “perfect” hysteresis; this does 
not change however that also at “imperfect” hysteresis the final 
state will depend on MH, and not only on //,. This would only be 
the case, when there was no hysteresis at all, but then every mag- 
netization-curve would be free from hysteresis, also that for a con- 
tinuous current alone, without use being made of an alternating current. 
Moreover I have convinced myself by some experiments that really 
the final state depends on the original intensity of the alternating 
current. The greater this is for a constant field H,, the stronger is 
the magnetization. If an alternating current is used we may therefore 
not say that the magnetization corresponds to the field HM, indepen- 
dently of the alternating current. 
January 1916. Physical Laboratory of Terrers Institute. 
Physics. — “On the ratio between the Zevman-ejject and the pressure- 
efjeet in the spectrum of nickel.’ By Dr. T. van LOHUIZEN. 
(Communicated by Prof. P. ZrEMAN.) 
(Communicated in the meeting of January 29, 1916). 
It will be known, that generally a connection is supposed to exist 
between the changes which spectrum lines undergo in a magnetic 
field and by an increase of pressure. In different spectra that are 
rich in lines the comparison between the magnitude of these two 
effects has been investigated among others by Kine?) for the spectra 
of Fe, Cr and Ti. 
As far as I know such an investigation has never yet been made 
for the spectrum of nickel. Therefore it seemed to me of some in- 
terest to determine also for this spectrum, which is so rich in lines, 
the ratio between the two effects. In order to use observations as 
equivalent as possible I took for the magnetie decompositions 
exclusively the observations of Miss GRAFTDIJK®), for the pressure 
1) A. S. Kiye. The correspondence between Zeeman-Effect and Pressure-Dis- 
placement for the Spectra of Iron, Chromium and Titanium. Astroph. J. 31. p. 433. 
1910. 
2) |. M. Grarrpijk. Magnetische splitsing van het Nikkel- en Cobaltspectrum en 
van het IJzerspectrum. Diss. Amsterdam 1911 and Arch. Neer]. ILA, Tome IL. 
ps 1922) 1912; 
