342 Mr. 0. Barus on the Change of the Order of Absolute 



even with marine glue, a beam of this substance, say a deci- 

 metre thick, would show about the same deformation initially 

 as a steel wire only a millimetre thick, ccet. par. So large 

 a mass of the cement is inconvenient to handle. I therefore 

 used a rod about 4 centim. thick and suitably apportioned the 

 torsion-couples in the two cases. The results are given in 

 Tables II. and III., where 2p is the diameter, I the length, of 

 the similarly twisted rods. This twist t is given in the first 

 column, and is proportional to the applied couples. N de- 

 notes the viscous motion at the index, at the time specified, 

 and is given in scale-parts (distance between mirror and scale 

 200 centim.). Reduction of N is not necessary, since the 

 present purposes are comparative. The steel wire is twisted 

 alternately in opposite directions to allow for the accommo- 

 dation. In Table II. this precaution is superfluous, the sub- 

 stance being a fluid. The three sets of data are merely given 

 to show the behaviour more fully. Other experiments made 

 with the cement may be omitted here. 



Table II. — Viscous Deformation of Hard Steel. Wire No. 1. 

 p = 0*40 centim. ; I = 30 centim. 



r. 



Time. 



NxlO 2 . 



T. 



Time. 



NxlO 2 . 



r. 



Time. 



NxlO 2 . 



minutes. 



cm. 





minutes. 



cm. 





minutes. 



cm. 



+5-7 







Twisted. 



-5-7 







Twisted. 



+5-8 







Twisted. 





2 









2 



- 





2 









3 



70 





3 



- 71 





4 



40 





4 



115 





4 



-125 





3 



72 





6 



187 





6 



-200 





6 



122 





8 



235 





8 



-258 





8 



160 





10 



278 





10 



-301 





10 



190 





12 



315 





12 



-340 





12 



212 



Table III. — Viscous Deformation of Marine Glue. 

 p = 2 centim. ; Z = 80 centim. 



r. 



Time. 



N X 10 2 . 



T. 



Time. 



NxlO 2 . 



T. 



Time. 



NxlO 2 . 





minutes. 



cm. 





minutes. 



cm. 





minutes. 



cm. 



*l-4 











1-4 











1-4 













2 



260 





2 



250 





2 



220 





3 



480 





3 



450 





3 



420 





4 



710 





4 



700 





4 



610 





5 



910 





5 



900 





5 

 6 



810 

 1010 



* This refers to the applied couple. The initial twist of the bar of marine 

 glue is practically zero. 



