502 Scientific Proceedings, Roijal Dublin Society. 



scale of baldness — that is, the number in the first column, or the load in 

 grammes per square centimetre which was on the lower end of the wire when 

 it was being heated — and as ordinates the corresponding values of (1) the 

 rigidity, and (2) the electrical conductivity, the points will be found in each 

 case to lie very approximately in a straight line. 



In order to observe the amount of twist on the end of the wire when it 

 was subjected to different longitudinal loads, and wlien placed in different 

 longitudinal magnetic fields, and with constant circular magnetism (that 

 is, with a maximum current through the wire in each ease at the rate of 

 100 amperes persq. cm.), the same long solenoid with accessories was used as 

 was employed in previous work.' 



The wire under test was fixed so as to hang vertically and as near as 

 possible in the middle of tlie solenoid, the total length of which was 237 cms. ; 

 the distance from the mirror on the vibrator or weight on the lower end of the 

 wire to the millimetre scale on which the twists or deflexions were read was 

 116-5 cms., and for every millimetre of deflexion on this scale the end of the 

 wire was twisted through an angle of 88 seconds. 



With a certain load on the end of the wire, and a given longitudinal 

 magnetic field round it, an electric current was sent through the wire, and its 

 value slowly increased up to tlie maximum of 100 amperes per sq. cm. ; and 

 the steady deflection read off the millimetre scale. The current was tlien 

 gradually diminished to zero, reversed, and again slowly increased to the 

 maximum, and the scale-reading once more observed on the other side of 

 zero ; the mean of these two readings was then taken as the true value of the 

 twist for that longitudinal magnetic field. 



The longitudinal load on the wire being kept the same, a similar process 

 was gone through for other fifteen different longitudinal magnetic fields up 

 to a maximum of 50 c.g.s. units. The load on the wire was now increased, 

 and a series of observations made similar to what was done for the first load ; 

 again the load on the wire was increased, and another series of observations 

 taken, giving results for three different loads in all. 



The above series of observations or tests were made on each of the five 

 tempered wires, which were each 226 cms. long and 0-163 cm. in diameter. 

 The results olatained are given in Table II. 



1 Scietit. Proc. Roy. Dub. Soc, vol. xii., pp. 11.5-183, and pp. 480-499. 



