1908-9.] Vibrational Neutral Points in Magnetised Iron. 
5 
Intensity of Vibrations. 
The intensity of the mechanical vibrations may be increased either by 
increasing the weight (W) of the steel ball or the vertical distance (D) 
through which it falls before striking the gong to which the experimental 
wire is soldered. When W and D are varied simultaneously so that the 
product of W x D° 7 is not changed, it is found that, under the same 
conditions, the induction change in the wire as measured by the ballistic 
galvanometer also remains unchanged within the limits of accuracy 
attainable in these experiments. The intensity of the vibrations is used 
in the sense that it varies with the function W x D 0-7 . In any series of 
experiments the same ball is used, the distance through which it falls 
alone being varied. 
Diagrams. 
Field (H), induction (B), and induction change (dB) are in C.G.S. units 
in all the diagrams. The intensity of the vibrations is proportional to 
W x D 0 ’ 7 , the weight (W) of the steel ball being in grams, the vertical 
distance (D) through which it falls in cms. All the points plotted are 
obtained by averaging the readings taken at symmetrical points in 
reference to the positive and negative cyclic extremes. They are, however, 
represented in all the diagrams as if taken in reference to the positive 
extremes. This applies both to cyclic fields and cyclic residual 
magnetisation. 
Cyclic Field. 
Experimental Data. — In fig. I. a series of nine trains of damped 
mechanical vibrations increasing in intensity are superposed in succession 
upon a sufficient number of points of that part of the hysteresis loop 
decreasing for H — 1*9, B = 3170 (cyclic extreme) to H = 0, B = 2000. The 
abscissae represent the intensity of the vibrations, increasing from W x D 0 ' 7 
= 2*2 to 10'4, superposed at eight values of field, viz. H = T9, 172, 1*6, 
F34, IT, 095, 052, and 0; the ordinates, the summation of the induction 
changes following thereon. Fig. I. taken in conjunction with Table I. 
which supplies the actual data from which two of the curves, viz. H = 1’34 
and I T, have been plotted, is, without further explanation, self-explanatory. 
Fig. I.a shows the same curves drawn to a slightly contracted horizontal 
scale, to a largely expanded vertical scale, in so far as they can be shown 
within the limits of about B = zk 60. The rectangles in dash lines show 
the contraction and expansion of the horizontal and vertical ordinates 
