336 
MR. C. CHREE OR THE EFFECTS OF PRESSURE 
application of load has effects very similar to those just described. It will appear, 
however, from fig. 42, § 88, that the critical fields at which the first application of a 
given load has no effect on the magnetisation are distinctly higher than the Vtt. t.ar t 
points for the cyclic applications of these loads. This figure also shows that the first 
application of a moderate load produces a very large increase of the magnetisation in 
weak fields, whereas in the strongest field of 84 C.G.S. units the effect is trifling. 
From fig. 40 it will be seen that in the cyclic state the effects of tension cycles on 
the magnetisation residual after a field of 3'33 C.G.S. units were of the same general 
character as appeared with an equal induced magnetisation. 
Soft annealed wires, when none but very small loads were used, were found by 
Professor Ewing to jiossess in weak fields a maximum of magnetisation with tension 
“ on,” agreeing so far with stretched wires. With greater loads the effects become 
reversed after the first application of the load. Professor Ewing attributes this to 
hysteresis, and shows that when tapped these wires behave as stretched wires with 
low ViLLARi points. 
From fig. 43, Plate 64, it will be seen that soft wires respond to the first application 
of tension in a precisely similar way to stretched wires, but have much lower critical 
fields. The phenomena accompanying the application of load cycles to a soft annealed 
wire possessed of the magnetism residual after the break of a field of '34 C.G.S. unit, 
are discussed in §§ 83-85 and shown in fig. 39. They are unquestionably of the same 
general character as those occurring with an equal induced magnetisation. 
Iron wires, both wlien stretched aud annealed, and a pianoforte steel wire stretched 
after annealing, were exposed by Professor Ewing to gradually increasing magnetising 
currents, and the curves connecting S* and >§ are given in his Plates 64 and 67. 
The specimens all showed Villa.e,i points of the second kind, which agreed with 
those of the first kind in being as a rule lower, the heavier the load. These critical 
fields, or magnetisations, of the second kind were distinctly higher than the corre¬ 
sponding ones of the first kind. 
Simultaneously observations were taken of the residual magnetisation whose results 
are shown in figures in Plates 67 and 68. In all the specimens the magnetisation 
residual after weak fields, and also its ratio to the induced magnetisation, were found 
to he largely increased by the presence of a load, the increase being greatest with the 
heaviest loads used. As the fields were raised the influence of the loads diminished, 
and in the annealed iron and the steel wires the residual magnetisation and its ratio 
to the induced became eventually less under the heavier loads than in the absence of 
a load. 
§ 12. In his papers in ‘ Phil. Trans.,’ A., 1888, Professor Ewing found that in fields 
from 0 to 116 C.G.S. units, the presence of a tension on a thin nickel wire diminished 
its induced and residual magnetisations, and also the ratio of the residual to the 
induced. Also cyclic changes of tension “ on ” and off'” ’■vere accompanied by 
