328 
PEOFESSOE W. THOMSON AXD DE. J. P. JOTLE ON THE 
Seeies VI. — Junction of wires ^th of an inch, in diameter. 
Velocities in the 
alternate experiments, 
in feet per second. 
Difference of 
thermal effect. 
Estimated effect 
of low velocity. 
Thermal effect 
of high velocity. 
Velocitv due 
to 1- C. 
93-1 and 39 
6-198 
6-042 
6-240 
190 
109-6 and 52-4 
0-239 
0-072 
0-311 
196-5 
133-96 and 58-3 
0-432 
0-100 
0-532 
183 
163-7 and 55-2 
0-654 
0-084 
0-738 
190-5 
From the above Tables it is manifest that the thermal effect increases nearly with the 
square of the velocity ; it is, however, a little greater at low velocities than accords with 
this law. Taking, therefore, the means of the foregoing results, and rejecting all those 
obtained from a velocity under 100 feet per second, we obtain the following sum- 
mary : — 
Material of the 
Diameter. 
Yelocity due 
whirled cylinder. 
to 1° Cent. 
Glass . . . 
. . . 0-26 
173-45 
Glass . 
. . . 0-48 
189 
Copper-iron 
. . . O-OI 
177-54 
Copper-iron 
. . . 0-025 
179-9 
Copper-iron 
. . . 0-057 
170-9 
Copper-iron 
. . . 0-II5 
190 
Mean .... 
. . 180-13 
It may be inferred from the above that the thermal effect is independent of the kind 
of material whirled, provided its surface is smooth ; and that it is likewise independent 
of the diameter of the cylinder moving in a direction perpendicular to its length. 
In the next experiments we whirled the junctions parallel to the direction of = 
motion. 
Seeies VII. 
Diameter 
of wire. 
Velocities in the 
alternate experiments, 
in feet per second. 
Difference 
of thermal 
effect. 
Estimated 
effect of 
low velocity. 
Thermal 
effect of 
liigh velocity. 
Velocity 
due to 
1° C. 
Cleans. 
•01 . 
-057 < 
•115 ■ 
■ 
123-4 and 45-2 
186-7 and 54-2 
126-5 and 39-6 
206-6 and 44 
100-5 and 44-8 
182-7 and 50 
6-415 
1-160 
0- 59 
1- 518 
0- 215 
1- 053 
0-064 
0-107 
0-058 
0-072 
0-053 
0-085 
6-479 
1-267 
0- 648 
1- 59 
0-268 
1-138 
178-3 
165-9 
157-1 
164 
194-1 
171-3 
J 172-1 
j 160-55 
\ 182-7 
J 
The general mean of the velocities due to 1° Cent, is therefore 171 '78, which is not 
notably different from the result obtained when the Ame was placed at right angles to 
the direction of motion. The absence of any considerable effect arising from the shape 
of the body whirled, Avas also shoAvn by the following results obtained AAdth a junction 
of flattened wires a quarter of an inch broad and one-thirtieth of an inch thick. 
