22 Barus and Strouhal— Viscosity of Steel. 
2. Tables 29, 29A, 30, contain a part of our results in which 
one steel wire is replaced by a wire of wrought iron, annealed 
or drawn as specified. That the amounts of torsion are equal 
in angle (#) is again assumed for convenience of designation 
only. p,is the radius of steel, o; of the iron wire. The applied 
couple twists soft iron beyond the limits of elasticity and the 
amount of instantaneous detorsion is here probably as large as 
4(¢,+¢,). In case of steel instantaneous detorsion is nearly 
Zero. 
TABLE 29.—APPARATUS I. 
R—293m.\ F—26m. 10-2" Rods: No: 3) (steel) annesled.a 40 Ommmis 
w= +180°; No. c, wrought iron, drawn, ~=—180°. 2p,=0:082™; 2o,=0-083e™. 
Date. | ¢x10°| fo |¢.x103|| Date. 6+103| ho | dox108 
ie | x 
17/7, 4220™| 1-955] 0-20) —0-387|/18/7, s®27™| 2177) 16-32] —0-165 
4 23 | 2:032/ 025] —0-310 2 24 2:122| 22-27] —0:220 
427 | 2113) 0°32) —0-229//1977) gh 37™| 2032/4148) —07310 
4 51 | 2°285 0°72} —0:057 12 19 9-025 | 44:18) —0:317 
520) | 2°342 1°20; +0:000] 5 10 2-014) 49:03] —0-328 
-362| 1: 020) - : 
pool | 2362) 1°88) +0°020)5077, ghogm| 1-984) 64-35/ 1 S0°368 
3 45 1-977! 71-62! —0-364 
* Adjusted r—b—f. 
TABLE 30.—AppaARATUS II. 
Rk=200™ D=27™; (<0:2™. Rods: No. 38, steel, annealed 450°, 14, 
w=+180°; No. d, wrought iron, soft, p=—180°. 2p,=0°082™; 2007112", 
| 
Date. ox 108 ho | 60x 10° Date. @x 102 “Ro | on x 1108 
16/7, 9240" (*) 0°00} (*) ||18/7, 8833™4| 0-146) 15°12] (0-153) 
9 48 0-714 0°13) —0 026) 230 0-151) 21-15) (07148) 
DO Ia eaiOe | iy eeeee an noe 12 20 | 0-119 (42-90), (0-180) 
5 AN | 0°750 8°23} ED) 5 10 _ 0-110) (47°73) (0°189) 
17/7, gh 4m O-7T31| 23°12} = 0°009) 90/7, 82 28" | - 0-082 (63-03)| (0-217) 
Thick iron wire replaced by thin) 3 44 | 0°064/(70°32)) (0°235) 
wire. Rod No. 9, wrought iron, soft;| | 
w=—180°; 20=0:083, | | | 
ET SX 0°755; *0:00; —0:019) | 
| 
5 30 0-745; 0°07/ —0-009 
5) 36 0°736| 0-17) +0-000 | 
6 00 0-718] 0-57| 40-018 | 
* Accident, new adjustment, data otherwise good. but distinguished by paren- 
theses ; 
+ Adjusted r—/—f. { Adjusted r+/+/, but the time not accurately noted. 
TABLE 30A.—APPARATUS II. 
R=202™; L=26™; 10-2. Rods: No, 50, annealed 350°. 15, p==+180°; 
No. &, wrought iron drawn, ~=—180°. 2p9;=0°084™; 290-082. 
Date. | @x103 | ho | box 108 | Date. @x103 | ho |x 108 
23/8, 2>00™ (*) 0:00 (*) 112778, 9" 10m 1-483} 9638) 0114 
2 13 2:052| 0722) —0:452 7 36 1:490 
2 20 1914 0°33 —0°314 98/8. gh Q]m -AQ5 13 107 
Seal 1599] 1:18} +0°001) 8; 6 55 Ae aye a 
5 37 1-417) 3°62) 0°183))- 
lion ; ‘ e 
ae a i rue Res Fi 40| 8078, 9 11™| 1-505] 16318) 0-095 
25/8, 98 05™|  1-435| 43-08| 0-165)/°1/8) A 19° | 0-085 
7 00 1-448] 53-02} 0:152 
4 08 1-469 2/9, - Us be 237°29| 0-074 
* Adjusted 7+/+/. 
