340 
MR. C. CHREE ON THE EFFECTS OF PRESSURE 
Preliminary Sketch of Phenomena Observed. 
§ 16. As the phenomena observed are somewhat complex, their mutual relationships 
might be hidden under the multiplicity of facts, which the full discussion of each 
separate phenomenon introduces. A brief outline of some of the more important and 
certain results will, it is hoped, serve as a key to the subsequent more complete 
discussion. 
It is important to notice that all the phenomena were observed in a given specimen 
of cobalt, magnetised by a current in a given coil, and that it was found by repeating 
several of the sets of observations at various periods of the research, that the character 
of the specimen had not to all appearance been altered during the process of the 
experiments. The importance of this, when an attempt shall be made to connect the 
phenomena together, and explain them as consequences of one or more fundamental 
principles, will be at once obvious to any one who has noticed the variety in the 
phenomena observed in different specimens of iron. 
At the same time, when various specimens of the same magnetic metal—or even 
of different magnetic metals—are exposed to gradually increasing magnetic fields, 
and curves drawn in which the absciss® give the strength of the field and the 
ordinates the intensity of magnetisation, experiment shows that the fields in which 
corresponding points of the several curves occur may widely differ, but that there 
exists a general resemblance in the form of the curves, which may be made much 
closer by properly altering the scale of absciss®. 
Thus, while the particular field at which a certain phenomenon presents itself in a 
particular specimen may so largely depend on the individual peculiarities of the 
specimen that it may be of little value as an isolated fact, yet the determination of 
the point on the curve vdiere the phenomenon occurs, and the position it occupies 
relative to the points where other phenomena occur, may lead to the recognition of 
general laws. 
Phenomena Observed in the Induced Magnetisation. 
§17. The “ Wendepurdct,” or point where the coefficient of induced magnetisation 
is a maximum, is a point in the curves that can easily l)e recognised. Very probably 
the most satisfactory comparison of the phenomena observed in different specimens 
would be obtained by expressing the magnetisation of each specimen in terms of the 
magnetisation it possesses at its Wendepunkt as a unit. The Wendepunkt of the 
specimen employed occurred in a field of about 35 C-G.S. units. 
For the reasons just stated, the relations of both the induced and residual magneti¬ 
sations to the strength of the field, though not a primary object of investigation, were 
observed under various conditions as to pressure. These relations, in the case of the 
induced magnetisation, are shown in figs. L-4 (Plate 15). 
The difference between the effects on the induced magnetisation of the first few and 
o 
