124 
PHYSICS: A. A. MICHELSON 
Proc. N. a. S. 
the value of temperature and pressure as functions of the distance from the 
center, we know but httle regarding the effect of these factors on either 
rigidity or viscosity. 
I. It was found that the temperature effect may be represented with 
considerable accuracy by the expression 
A = + 
in which P is the applied stress, G the temperature and K and h constants. 
For room temperature the values oihQ = h are given in table IV. 
If we take h — 0.2 as fairly representative 
52 = Pe -^^{1 — e- Vr). (The unit P = 100 gm.) 
so that G the couple = Pr gm. cm. Thus we get for the displacement 
after a sufficiently long time 
5 = Pe'^'and- = - 
fii P 
TABLE I 
p 
S/P 
0 
1.0 
1 
1.2 
10 
7.0 
50 
20000.0 
showing the very great increase in importance of the elastico- viscous term 
for large stresses. The same is also true for the purely viscous term. 
The following table gives the ratio n^/ni for twenty- two materials 
showing that there are certainly two elasticities — one of which is not 
accompanied by viscosity and the second is thus affected. In every 
case excepting that of sealing wax, where the ratio is unity, the second 
elasticity is much greater than the first, and in some cases enormously 
greater. 
TABLE II 
Tin 
Zinc 
Marble 
Limestone. 
Ebonite. . . 
Iron 
Steel 
Copper 
Aluminum. 
Talc 
Glass 
60 
70 
45 
30 
8 
2200 
12000 
8 
4400 
200 
100 
Slate 
Shale 
Soapstone. . . 
Lead 
Cadmium . . . 
Gold 
Magnesium . 
Bapelite .... 
Ivory 
Silver 
Sealing Wax , 
150 
50 
35 
40 
65 
150 
250 
7 
50 
80 
1 
