ON MAGNETOS'I'RICTION. 23 



project out of tlie openiiigs, and its axis is kept in coincidence witli 

 that of the tube. The axis of the magnetizing coil, which is all the 

 while water jacketed, also coincides with that ()f the volumenometer 

 during the experiments, so that the effect of the mechanical force and 

 the non-uniformity of the field (the length of coil being 30, while that 

 of the ovoid is 20 cm.) will not enter the measured results. 



The motion of the capillary meniscus was noted by means of a 

 microscope provided with a micrometer ocular. The magnifying 

 power of the microscope was generally so chosen, that the range of 

 motion during the experiment lay within the field of view\ Although 

 the magnetizing coil was water jacketed, the lack of temperature com- 

 pensation, as in the experiments on the length change, made it desir- 

 able to notice the motion of the liquid shortly after making the 

 current. In some of the metals, the change was generally almost in- 

 stantaneous, but in a few specimens we noticed a distinct time-lag. 



As announced by Quincke,^ ^ change of volume in the liquid 

 filling the volumenometer may be caused by tiie pressure in the 

 magnetic field. To guard against this point, we have specially 

 examined the volumenometer readings by simply filling it with water 

 or ferric chloride, and did not find the effect within the range of field 

 used in the present experiment, as might well be expected, as the 

 pressure is proportional to the square of the field strength. 



Cast Steel. The metal shows increase of volume in fields up to 

 about 2000. The following gives the measured change. 



1) Quincke, Sitzimgsberichte d. Berliner Akademie d. Wissenschaften, 20= P- 391, 1900. 



