48 



Mr. T. Gray on Silk v. Wire Suspensions in 

 Magnetic Method. 



.2 



£'■§ 



Hi 



fe ea- 

 ed f-i 



i 2 



03 d 



Deflection per turn 

 of torsion-head on 



a scale of milli- 

 metres. Magnetic 

 field =-153. 



Distance of the 

 scale from the 

 mirror, in centi- 

 metres. 



Torsional rigidity, 

 in C.Gr.S. units, 

 of a length of 

 1 centim. 



Young's modulus 



for the fibre, 



weight in 



grammes*. 



905 

 920 



8-45 

 9-55 



00010 

 0-0009 

 000145 

 0-0015 



8-0 



8-0 



21-0 



215 



117-0 

 1170 

 1170 



117-0 



•00143 

 •00090 

 •00216 

 •00250 



75-4 

 61-3 



65-6 

 735 



The following curve illustrates an experiment, and shows 

 how nearly proportional the first deflection is to the torsion even 

 after the elastic limit of the fibre has been far exceeded. In 



the first part of the curve the ordinates are the scale-readings, 

 the abscissae the angle turned through by the torsion-head, 



* This is the ratio of the product of the pull applied to the fibre, and the 

 length of the fibre, to the elongation produced by the pull, or, if E be the 

 weight applied X length of fibre 

 elongation. 



modulus, E = 



