122 Coefficient of Normal Viscosity of Metals. 



Table V. Carbon steels (20 c C.). 



Ourv< 



;No 



1. 



2- 



3. 



4 



5. 







C per cent.... 



0-18 



0-38 



0-67 



1-17 



1-75 





Si „ „ .... 



0-098 



0-17 



0-20 



0-31 



0-068 



Composition 

 of Bauds. 



Mn„ „ ... 

 P „ „ ... 



0-105 

 0-006 



0-40 

 0-016 



0-53 



0-48 

 0012 



0-14 

 0-013 





s „ t , ... 



0-033 



0033 





0-011 



011 





On „ „ ... 



0123 



0-114 



trace 



0-101 



0-092 



Total impurity 



excl. Carbon. 



0-37 



0-74 



073 



0-91 



0-33 



Dimension 

 of Bands. 



a cm 



0726 



0-0892 



0-123 



0-0811 



0-0725 





0-489 



0-497 



0-500 



0-497 



0-480 







x xio 3 



1-23 



1-76 



4-73 



1-60 



1-79 



Before 



annealing. 



T sec 



?XlO- 8 



0-750 

 4-91 



0-688 

 5-12 



0-479 

 5-93 



0-708 

 5-06 



0-766 



7-20 



Aunealed at 

 850° 



A Xl0 3 



Tsec 



0-73 

 07f6 



1-20 

 0-684 



3-45 

 0-481 



1-34 

 0701 







^XlO- 8 



2-68 



3-51 



430 



4-27 





/=26-0cm. M=199-4gr. 



Thus, except rolled zinc, the coefficient of normal viscosity 

 of different metals here investigated is o£ the order of 

 the order of magnitude of 1-10 x 10 8 O.Gr.S. units. The 

 large value of f in the case of zinc is to be expected from its- 

 low melting-point ; because, from the analogy of the change 

 of tangential viscosity with temperature, it follows that in 

 approaching the melting-point of a metal, f rapidly increases, 

 and in the case of zinc, room temperature is much nearer to 

 its melting-point than in other metals. 



Generally speaking, annealing causes the diminution of 

 the coefficient of normal viscosity. In the case of aluminium, 

 silver, magnesium, and nickel, the logarithmic decrement of 

 annealed specimens is greatly affected by the amplitude of 

 oscillation — that is, it increases at first linearly, then some- 

 what rapidly, and after passing through an inflexion point, 

 tends to an asymptotic value (PL VI.) . Hence, in these 

 metals, the estimation of the logarithmic decrement corre- 

 sponding to zero amplitude, and therefore the value of 

 tangential viscosity, is somewhat uncertain. Since the 

 annealing produces a growth of its crystalline structure, and 



