126 
PHYSICS: A. A. MICHELSON 
Proc. N. a. S. 
Thus if P be given a constant value for a time and then changed to 
Pi the corresponding value of the viscous term would be 
53 = (Fo^o + F,tf/\ 
If the first stress be considerable and act for a long time, the effect 
of the second stress is negligible. 
Following is a provisional table of the constants which appear in the 
formula for the torsional strain at room temperature. 
S = + ^2 (1 — e-«V7) + A^f + in which A = CPe^^\ P is the 
weight acting on a pulley of radius 5 cm. The unit of weight being 100 
grams and the unit of time one minute. The specimen is a cylindrical rod 
7.5 cm. long and 4 mm. in diameter. 
The term A4, which may be termed the "lost motion" should probably 
be considered as a part of the viscous term — but with a very small ex- 
ponent r so that the whole viscous term may be represented by 
S3 = CsPe'^'^if + Bf). 
TABLE IV 
Ci 
C2 
c 
Ci 
hi 
h2 
h3 
hi 
a 
p 
Tin slowly cooled 
660 
20 
0 
3. 
0 
1 
0 
0 
10 
1 
0 
3 
5 
4 
5 
0 
8 
0.6 
Tin quickly cooled 
640 
8 
0 
0 
6 
0.3 
0 
00 
1 
8 
3 
8 
4 
6 
0 
8 
0.6 
Zinc slowly cooled 
312 
3 
0 
3 
4 
2 
0 
0 
00 
0 
4 
0 
3 
0 
8 
1 
0 
0.5 
Zinc quickly cooled 
300 
8 
4 
3 
0 
0 
00 
0 
00 
0 
4 
0 
6 
1 
8 
1 
0 
0.5 
Marble 
840 
18 
0 
40 
0 
34 
0 
0 
14 
1 
8 
0 
8 
0 
3 
1 
1 
0.2 
Limestone 
600 
20 
0 
9 
0 
11 
0 
0 
10 
0 
3 
0 
3 
0 
8 
1 
2 
0.3 
Ebonite, first determ.. . . 
13 X 103 
1600 
600? 
0? 
0 
00 
0 
1 
0 
0 
0 
6 
0.5 
Ebonite, second determ.. 
13 X 103 
1800 
0 
750 
0 
0 
0 
0 
00 
0 
1 
0 
2 
0 
9 
0.7 
Soft Iron Annealed 
145 
0 
06 
0 
00 
0 
15 
0 
00 
0 
1 
0 
1 
1 
0 
0.2 
Soft Iron unannealed. . . . 
155 
0 
08 
0 
00 
0 
15 
0 
04 
0 
1 
0 
1 
1 
0 
0.2 
Tool steel, annealed 
144 
0 
01 
0 
00 
0 
10 
0 
00 
0 
2 
0 
1 
0 
4 
0.3 
Tool steel, glass hard. . . . 
143 
0 
14 
0 
26 
0 
07 
0 
00 
0 
0 
03 
0 
06 
0 
4 
0.4 
Copper, annealed 
250 
1 
3 
0 
00 
0 
75 
0 
06 
0 
1 
1 
8 
1 
2 
0 
5 
0.3 
Aluminum, annealed .... 
440 
0 
1 
0 
00 
0 
9 
0 
00 
1 
0 
2 
5 
1 
4 
1 
0 
0.3 
Talc, parallel cleavage . . 
1340 
4 
0 
20 
0 
110 
00 
0 
60 
3 
0 
1 
4 
1 
2 
1 
0 
0.3 
Slate, parallel cleavage . . 
382 
2 
0 
0 
4 
0 
6 
0 
01 
0 
3 
0 
7 
0 
6 
1 
2 
0.3 
Slate, perp. to cleavage.. 
400 
4 
0 
1 
6 
1 
0 
0 
03 
0 
3 
0 
00 
0 
8 
1 
5 
0.6 
3 X 10^ 
2 X 
104 
? 
? 
0 
00 
0 
0 
00 
00 
00 
0 
7 
? 
Glass (plate) 
446 
3 
0 
0 
00 
4 
0 
0 
00 
0 
0 
00 
00 
00 
0 
5 
Glass (lead) 
425 
5 
6 
0 
00 
0 
1 
0 
00 
0 
0 
00 
00 
15 
1 
4 
Shale, parallel cleavage. . 
400 
8 
4 
1 
0 
1 
2 
0 
02 
0 
16 
00 
35 
6 
1 
2 
0.4 
Lead 
1500 
40 
0 
7 
0 
4 
0 
0 
00 
0 
2 
1 
9 
3 
6 
1 
1 
0.4 
Cadmium 
460 
70 
0 
5 
4 
2 
4 
0 
00 
0 
2 
0 
6 
0 
8 
1 
0 
0.5 
Gold 
450 
3 
0 
0 
2 
1 
0 
0 
00 
0 
4 
0 
2 
0 
3 
1 
0 
0.3 
Magnesium 
2300 
9 
4 
8 
0 
50 
0 
0 
00 
0 
25 
0 
4 
0 
6 
1 
2 
0.3 
Bakellite 
7400 
960 
0 
14 
0 
0 
00 
0 
00 
0 
12 
0 
2 
1 
2 
0.8 
Ivory 
104 
320 
0 
3 
0 
0 
00 
0 
00 
0 
10 
0 
2 
0 
8 
0.6 
Silver 
480 
6 
0 
2 
0 
0 
4 
0 
00 
0 
06 
0 
1 
0 
2 
1 
0 
0.3 
^ Mon. Not. Roy. Astron. Soc, 77, No. 5. 
2 These Proceedings, 3, No. 5. 
3 The strains in these experiments were torsional, thus involving only the rigidity 
